{"id":2973,"date":"2013-08-29T12:39:48","date_gmt":"2013-08-29T03:39:48","guid":{"rendered":"http:\/\/peta.okechan.net\/blog\/?p=2973"},"modified":"2013-08-29T12:39:48","modified_gmt":"2013-08-29T03:39:48","slug":"5-2-4-ifthenelse%e3%81%ae%e3%81%9f%e3%82%81%e3%81%aellvm-ir","status":"publish","type":"post","link":"https:\/\/peta.okechan.net\/blog\/archives\/2973","title":{"rendered":"5.2.4. if\/then\/else\u306e\u305f\u3081\u306eLLVM IR"},"content":{"rendered":"

LLVM\u306b\u3088\u308b\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u8a00\u8a9e\u306e\u5b9f\u88c5\u30c1\u30e5\u30fc\u30c8\u30ea\u30a2\u30eb\u65e5\u672c\u8a9e\u8a33<\/a>
\n\u7b2c5\u7ae0 \u4e07\u83ef\u93e1: \u8a00\u8a9e\u306e\u62e1\u5f35: \u5236\u5fa1\u30d5\u30ed\u30fc
\n\u7b2c2.4\u7bc0 if\/then\/else\u306e\u305f\u3081\u306eLLVM IR<\/a><\/p>\n

\u3053\u308c\u3067\u3001\u69cb\u6587\u89e3\u6790\u3057\u3066AST\u3092\u69cb\u7bc9\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u3063\u305f\u3002
\n\u6700\u5f8c\u306e\u30d1\u30fc\u30c4\u306f\u3001LLVM\u30b3\u30fc\u30c9\u306e\u751f\u6210\u6a5f\u80fd\u306e\u8ffd\u52a0\u3067\u3042\u308b\u3002
\n\u3053\u308c\u306fif\/then\/else\u306e\u5b9f\u4f8b\u306b\u304a\u3051\u308b\u4e00\u756a\u8208\u5473\u6df1\u3044\u90e8\u5206\u3067\u3042\u308b\u3002
\n\u306a\u305c\u306a\u3089\u3053\u308c\u304c\u3001\u65b0\u3057\u3044\u30b3\u30f3\u30bb\u30d7\u30c8\u3092\u7d39\u4ecb\u3059\u308b\u30b9\u30bf\u30fc\u30c8\u5730\u70b9\u3060\u304b\u3089\u3067\u3042\u308b\u3002
\n\u524d\u7bc0\u307e\u3067\u306e\u30b3\u30fc\u30c9\u306f\u4ee5\u524d\u306e\u7ae0\u3067\u5341\u5206\u306b\u89e3\u8aac\u3055\u308c\u3066\u3044\u308b\u3002<\/p>\n

\u6211\u3005\u304c\u3084\u308a\u305f\u3044\u4e8b\u3092\u30b3\u30fc\u30c9\u306b\u884c\u308f\u305b\u308b\u305f\u3081\u306b\u3001\u4ee5\u4e0b\u306e\u7c21\u5358\u306a\u4f8b\u3092\u898b\u3066\u3001\u8003\u3048\u3066\u307f\u3088\u3046\u3002<\/p>\n

extern foo();\r\nextern bar();\r\ndef baz(x) if x then foo() else bar();<\/pre>\n
\u3082\u3057\u6700\u9069\u5316\u7121\u3057\u306a\u3089\u3001\u4e0a\u306e\u30b3\u30fc\u30c9\u306f\u4e07\u83ef\u93e1\u306b\u3088\u308a\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u306a\u308b\u306f\u305a\u3067\u3042\u308b\u3002<\/p>\n
declare double @foo()\r\n\r\ndeclare double @bar()\r\n\r\ndefine double @baz(double %x) {\r\nentry:\r\n  %ifcond = fcmp one double %x, 0.000000e+00\r\n  br i1 %ifcond, label %then, label %else\r\n\r\nthen:       ; preds = %entry\r\n  %calltmp = call double @foo()\r\n  br label %ifcont\r\n\r\nelse:       ; preds = %entry\r\n  %calltmp1 = call double @bar()\r\n  br label %ifcont\r\n\r\nifcont:     ; preds = %else, %then\r\n  %iftmp = phi double [ %calltmp, %then ], [ %calltmp1, %else ]\r\n  ret double %iftmp\r\n}<\/pre>\n
\u5236\u5fa1\u30d5\u30ed\u30fc\u30b0\u30e9\u30d5\u3092\u8996\u899a\u5316\u3059\u308b\u305f\u3081\u306b\u3001LLVM\u306e”opt”\u30c4\u30fc\u30eb\u306e\u30a4\u30ab\u30b7\u305f\u6a5f\u80fd\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u304c\u51fa\u6765\u308b\u3002
\n\u4e0a\u8a18\u3092t.ll\u306b\u4fdd\u5b58\u3057\u305f\u3068\u3057\u3066\u3001”llvm-as <  t.ll | opt -analyze -view-cfg\"\u3092\u5b9f\u884c\u3059\u308b\u3068\u3001\u30a6\u30a4\u30f3\u30c9\u30a6\u304c\u7acb\u3061\u4e0a\u304c\u308a\u3001\u6b21\u306e\u3088\u3046\u306a\u30b0\u30e9\u30d5\u304c\u898b\u308c\u308b\u306f\u305a\u3067\u3042\u308b\u3002\n\u8a33\u6ce8: LLVM\u3092\u30bd\u30fc\u30b9\u304b\u3089\u30b3\u30f3\u30d1\u30a4\u30eb\u3057\u3066\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3057\u305f\u3060\u3051\u3067\u4ed6\u306f\u4f55\u3082\u8a2d\u5b9a\u3057\u3066\u306a\u3044Mac\u3067\u306f\u3001\u4e0a\u8a18\u306e\u30b3\u30de\u30f3\u30c9\u3060\u3051\u3067\u306f\u4f55\u306e\u30a6\u30a4\u30f3\u30c9\u30a6\u3082\u958b\u304b\u306a\u304b\u3063\u305f\u304c\u3001\/tmp\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306b.dot\u30d5\u30a1\u30a4\u30eb\u304c\u51fa\u529b\u3055\u308c\u3001\u305d\u308c\u3092Graphviz\u3067\u958b\u304f\u3068\u540c\u3058\u3082\u306e\u304c\u898b\u308c\u305f\u3002<\/em><\/p>\n
\"cfgbaz-cfac13\"<\/a><\/p>\n
\u3053\u306e\u30b0\u30e9\u30d5\u3092\u5f97\u308b\u65b9\u6cd5\u306f\u4ed6\u306b\u3082\u3042\u308b\u3002
\n\u5b9f\u969b\u306e\u30b3\u30fc\u30c9\u306e\u4e2d\u306b\u3001\u201cF->viewCFG()\u201d \u304b \u201cF->viewCFGOnly()\u201d\u306e\u547c\u3073\u51fa\u3057\uff08F\u306fFunction*\uff09\u3092\u8ffd\u52a0\u3057\u3066\u518d\u30b3\u30f3\u30d1\u30a4\u30eb\u3059\u308b\u304b\u3001\u30c7\u30d0\u30c3\u30ac\u3067\u201cF->viewCFG()\u201d \u304b \u201cF->viewCFGOnly()\u201d\u3092\u547c\u3073\u51fa\u3059\u3068\u540c\u3058\u30b0\u30e9\u30d5\u304c\u5f97\u3089\u308c\u308b\u3002
\nLLVM\u306f\u3001\u3044\u308d\u3093\u306a\u30b0\u30e9\u30d5\u3092\u8996\u899a\u5316\u3059\u308b\u305f\u3081\u306e\u7d20\u6674\u3089\u3057\u3044\u6a5f\u80fd\u3092\u305f\u304f\u3055\u3093\u6301\u3063\u3066\u3044\u308b\u3002<\/p>\n
\u751f\u6210\u3055\u308c\u308b\u3079\u304d\u30b3\u30fc\u30c9\u306b\u8a71\u3092\u623b\u3059\u3068\u3001\u305d\u308c\u306f\u6975\u3081\u3066\u30b7\u30f3\u30d7\u30eb\u3067\u3042\u308b\u3002
\nentry\u30d6\u30ed\u30c3\u30af\u306f\u6761\u4ef6\u5f0f\u3092\u8a55\u4fa1\u3057\uff08\u4e0a\u8a18\u306e\u4f8b\u3067\u306fx\u304c\u6761\u4ef6\u5f0f\u3067\u3042\u308b\uff09\u3001\u305d\u306e\u7d50\u679c\u3092”fcmp one”\u547d\u4ee4\uff08”one”\u306f”Ordered and Not Equal”\uff09\u3092\u7528\u3044\u30660.0\u3068\u6bd4\u8f03\u3059\u308b\u3002
\n\u3053\u306e\u5f0f\u306e\u7d50\u679c\u3092\u5143\u306b\u3001\u30b3\u30fc\u30c9\u306f”then”\u304b”else”\u30d6\u30ed\u30c3\u30af\u3078\u30b8\u30e3\u30f3\u30d7\u3059\u308b\u3002
\n\u305d\u308c\u305e\u308c\u306e\u30d6\u30ed\u30c3\u30af\u306ftrue\u3082\u3057\u304f\u306ffalse\u306e\u5834\u5408\u306e\u5f0f\u3092\u542b\u3093\u3067\u3044\u308b\u3002
\n\u8a33\u6ce8: Ordered and Not Equal\u306eOrdered\u306b\u3064\u3044\u3066\u3002
\nOrdered \u306f2\u3064\u306e\u30aa\u30da\u30e9\u30f3\u30c9\u306e\u3046\u3061\u3069\u3061\u3089\u3082QNAN\u3067\u306f\u306a\u3044\u3068\u3044\u3046\u4e8b\u3092\u610f\u5473\u3059\u308b\u3002
\n\uff08QNAN\u3068\u3044\u3046\u306e\u306f\u591a\u5206\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306b\u304a\u3051\u308bQuiet NaN\u306e\u3053\u3068\u304b\u3068\u601d\u308f\u308c\u308b\u3002\uff09
\nOrdered\u304c\u3042\u308b\u3068\u3044\u3046\u3053\u3068\u306fUnordered\u3082\u3042\u308a\u3001\u305d\u3061\u3089\u306f\u7247\u65b9\u306e\u30aa\u30da\u30e9\u30f3\u30c9\u304cQNAN\u304b\u3082\u3057\u308c\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u3092\u610f\u5473\u3059\u308b\u3002
\nfcmp one <ty> <op1> <op2> \u306e\u5834\u5408\uff08Ordered and Not Equal\u306e\u5834\u5408\uff09\u3001\u4e21\u65b9\u306e\u30aa\u30da\u30e9\u30f3\u30c9\u304cQNAN\u3067\u306f\u306a\u304f\u3001\u306a\u304a\u304b\u3064op1\u3068op2\u304c\u7b49\u3057\u304f\u306a\u3044\u3068\u304d\u306btrue\u3092\u8fd4\u3059\u3002
\nfcmp une <ty> <op1> <op2> \u306e\u5834\u5408\uff08Unordered and Not Equal\u306e\u5834\u5408\uff09\u3001\u7247\u65b9\u306e\u30aa\u30da\u30e9\u30f3\u30c9\u304cQNAN\u3001\u3082\u3057\u304f\u306fop1\u3068op2\u304c\u7b49\u3057\u304f\u306a\u3044\u3068\u304d\u306btrue\u3092\u8fd4\u3059\u3002<\/em><\/p>\n
then\/else\u30d6\u30ed\u30c3\u30af\u306e\u5b9f\u884c\u304c\u7d42\u308f\u308c\u3070\u3001\u305d\u308c\u30892\u3064\u306e\u679d\u5206\u304b\u308c\u306f\u3001if\/then\/else\u306e\u5f8c\u306b\u3042\u308b\u30b3\u30fc\u30c9\u3092\u5b9f\u884c\u3059\u308b\u305f\u3081\u306b\u3001ifcont\u30d6\u30ed\u30c3\u30af\u306b\u5408\u6d41\u3059\u308b\u3002
\n\u3053\u306e\u4f8b\u306e\u5834\u5408\u3060\u3068\u3001\u6b8b\u3063\u3066\u308b\u306e\u306f\u95a2\u6570\u306e\u547c\u3073\u51fa\u3057\u5143\u306b\u623b\u308b\u3068\u3044\u3046\u3053\u3068\u3060\u3051\u3067\u3042\u308b\u3002
\n\u3053\u3053\u3067\u7591\u554f\u304c\u601d\u3044\u6d6e\u304b\u3076\u3002
\n\u3069\u3063\u3061\u306e\u5f0f\u306e\u7d50\u679c\u3092\u8fd4\u3059\u304b\u306b\u3064\u3044\u3066\u305d\u306e\u30b3\u30fc\u30c9\u306f\u3069\u3046\u3084\u3063\u3066\u77e5\u308b\u306e\u304b\uff1f<\/p>\n
\u3053\u306e\u7591\u554f\u3078\u306e\u7b54\u3048\u306f\u3001\u91cd\u8981\u306aSSA\u547d\u4ee4\u3067\u3042\u308bphi\u547d\u4ee4\u306b\u95a2\u4fc2\u3059\u308b\u3002
\n\u3082\u3057\u3001SSA\u306b\u95a2\u3057\u3066\u3088\u304f\u77e5\u3089\u306a\u3051\u308c\u3070\u3001Wikipedia\u306e\u8a18\u4e8b\uff08http:\/\/en.wikipedia.org\/wiki\/Static_single_assignment_form<\/a>\uff09\u304c\u826f\u3044\u5c0e\u5165\u306b\u306a\u308b\u3057\u3001SSA\u306b\u5bfe\u3059\u308b\u4ed6\u306e\u69d8\u3005\u306a\u8aac\u660e\u306b\u3064\u3044\u3066\u597d\u304d\u306a\u691c\u7d22\u30a8\u30f3\u30b8\u30f3\u3067\u63a2\u3059\u3053\u3068\u3082\u51fa\u6765\u308b\u3002
\n\u8a33\u6ce8: \u65e5\u672c\u8a9e\u3060\u3068\u9759\u7684\u5358\u4e00\u4ee3\u5165\u3067\u691c\u7d22\u3059\u3079\u3057\u3002<\/em><\/p>\n
\u7c21\u5358\u306b\u8aac\u660e\u3059\u308b\u3068\u3001phi\u547d\u4ee4\u306e\u5b9f\u884c\u306b\u306f\u3001\u5236\u5fa1\u304c\u3069\u306e\u30d6\u30ed\u30c3\u30af\u304b\u3089\u6765\u305f\u306e\u304b\u899a\u3048\u3066\u304a\u304f\u4e8b\u304c\u5fc5\u8981\u3068\u306a\u308b\u3002
\nphi\u547d\u4ee4\u306f\u3001\u5165\u3063\u3066\u304d\u305f\u5236\u5fa1\u30d6\u30ed\u30c3\u30af\u306b\u5408\u81f4\u3059\u308b\u5024\u3092\u53d7\u3051\u53d6\u308b\u3002
\n\u3053\u306e\u5834\u5408\u3001\u5236\u5fa1\u304c”then”\u30d6\u30ed\u30c3\u30af\u304b\u3089\u6765\u305f\u5834\u5408\u3001phi\u547d\u4ee4\u306fcalltmp\u306e\u5024\u3092\u53d7\u3051\u53d6\u308b\u3002
\n\u3082\u3057\u5236\u5fa1\u304c”else”\u30d6\u30ed\u30c3\u30af\u304b\u3089\u6765\u305f\u5834\u5408\u3001phi\u547d\u4ee4\u306fcalltmp1\u306e\u5024\u3092\u53d7\u3051\u53d6\u308b\u3002<\/p>\n
\u3053\u306e\u6642\u70b9\u3067\u3001\u3042\u306a\u305f\u306f\u591a\u5206\u3053\u3046\u8003\u3048\u59cb\u3081\u308b\u3060\u308d\u3046\u3002
\n\u300c\u306a\u3093\u3066\u3053\u3063\u305f\uff01LLVM\u3092\u4f7f\u7528\u3059\u308b\u305f\u3081\u306b\u3001\u30aa\u30ec\u306e\u30b7\u30f3\u30d7\u30eb\u3067\u30a8\u30ec\u30ac\u30f3\u30c8\u306a\u30d5\u30ed\u30f3\u30c8\u30a8\u30f3\u30c9\u3092\u3001SSA\u5f62\u5f0f\u3092\u751f\u6210\u3059\u308b\u3088\u3046\u306b\u3057\u306a\u304d\u3083\u3044\u3051\u306a\u3044\u3063\u3066\u3053\u3068\u304b\uff01\u300d
\n\u5e78\u904b\u306b\u3082\u305d\u3046\u3067\u306f\u306a\u3044\u3002
\n\u3082\u306e\u51c4\u304f\u91cd\u8981\u306a\u7406\u7531\u304c\u7121\u3044\u9650\u308a\u3001SSA\u69cb\u7bc9\u306e\u30a2\u30eb\u30b4\u30ea\u30ba\u30e0\u3092\u30d5\u30ed\u30f3\u30c8\u30a8\u30f3\u30c9\u306b\u5b9f\u88c5\u3059\u3079\u304d\u3067\u306f\u306a\u3044\u3068\u3001\u6211\u3005\u306f\u5f37\u304f\u30a2\u30c9\u30d0\u30a4\u30b9\u3059\u308b\u3002
\n\u5b9f\u969b\u554f\u984c\u3068\u3057\u3066\u3001\u5e73\u5747\u7684\u306a\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u8a00\u8a9e\u306e\u305f\u3081\u306b\u66f8\u304b\u308c\u305f\u30b3\u30fc\u30c9\u306e\u307e\u308f\u308a\u3067\u6d6e\u304b\u3093\u3067\u3044\u308b\u3001phi\u30ce\u30fc\u30c9\u3092\u5fc5\u8981\u3068\u3059\u308b\u304b\u3082\u3057\u308c\u306a\u30442\u7a2e\u985e\u306e\u5024\u304c\u3042\u308b\u3002
\n\uff08In practice, there are two sorts of values that float around in code written for your average imperative programming language that might need Phi nodes:\uff09<\/p>\n
1. \u30e6\u30fc\u30b6\u5909\u6570\u3092\u307e\u304d\u3053\u3080\u30b3\u30fc\u30c9\u3002x = 1; x = x + 1;
\n2. \u3053\u306e\u5834\u5408\u306ephi\u30ce\u30fc\u30c9\u306e\u3088\u3046\u306a\u3001AST\u306e\u69cb\u9020\u4e0a\u6697\u9ed9\u7684\u306b\u5b58\u5728\u3059\u308b\u5024\u3002<\/p>\n
\u3053\u306e\u30c1\u30e5\u30fc\u30c8\u30ea\u30a2\u30eb\u306e\u7b2c7\u7ae0\uff08\u5909\u66f4\u53ef\u80fd\u306a\u5909\u6570\uff09\u3067\u306f\u30011\u306b\u3064\u3044\u3066\u6df1\u304f\u8aac\u660e\u3059\u308b\u3002
\n\u3053\u306e\u3088\u3046\u306a\u5834\u5408\u3092\u5236\u5fa1\u3059\u308b\u305f\u3081\u306bSSA\u3092\u69cb\u7bc9\u3059\u308b\u5fc5\u8981\u304c\u306a\u3044\u3001\u3068\u3044\u3046\u3053\u3068\u3092\u4eca\u306f\u5358\u306b\u4fe1\u3058\u3066\u6b32\u3057\u3044\u3002
\n2\u306b\u3064\u3044\u3066\u306f\u30011\u3068\u540c\u3058\u304f\u7b2c7\u7ae0\u3067\u8aac\u660e\u3059\u308b\u6280\u6cd5\u304b\u3092\u4f7f\u3046\u304b\u3001\u7c21\u5358\u306bphi\u30ce\u30fc\u30c9\u3092\u76f4\u63a5\u633f\u5165\u3059\u308b\u65b9\u6cd5\u304c\u9078\u3079\u308b\u3002
\n\u3053\u306e\u5834\u5408\u3001phi\u30ce\u30fc\u30c9\u3092\u751f\u6210\u3059\u308b\u306e\u306f\u5b9f\u306b\u7c21\u5358\u306a\u306e\u3067\u3001\u6211\u3005\u306f\u76f4\u63a5\u633f\u5165\u3059\u308b\u65b9\u6cd5\u3092\u9078\u629e\u3059\u308b\u3002<\/p>\n
\u3088\u3057\u3001\u5341\u5206\u306a\u52d5\u6a5f\u3068\u6982\u89b3\u3092\u5f97\u305f\u3068\u3053\u308d\u3067\u3001\u30b3\u30fc\u30c9\u3092\u751f\u6210\u3057\u3088\u3046\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
LLVM\u306b\u3088\u308b\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u8a00\u8a9e\u306e\u5b9f\u88c5\u30c1\u30e5\u30fc\u30c8\u30ea\u30a2\u30eb\u65e5\u672c\u8a9e\u8a33<\/a>
\n\u7b2c5\u7ae0 \u4e07\u83ef\u93e1: \u8a00\u8a9e\u306e\u62e1\u5f35: \u5236\u5fa1\u30d5\u30ed\u30fc
\n\u7b2c2.4\u7bc0 if\/then\/else\u306e\u305f\u3081\u306eLLVM IR<\/a><\/p>\n
\u3053\u308c\u3067\u3001\u69cb\u6587\u89e3\u6790\u3057\u3066AST\u3092\u69cb\u7bc9\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u3063\u305f\u3002
\n\u6700\u5f8c\u306e\u30d1\u30fc\u30c4\u306f\u3001LLVM\u30b3\u30fc\u30c9\u306e\u751f\u6210\u6a5f\u80fd\u306e\u8ffd\u52a0\u3067\u3042\u308b\u3002
\n\u3053\u308c\u306fif\/then\/else\u306e\u5b9f\u4f8b\u306b\u304a\u3051\u308b\u4e00\u756a\u8208\u5473\u6df1\u3044\u90e8\u5206\u3067\u3042\u308b\u3002
\n\u306a\u305c\u306a\u3089\u3053\u308c\u304c\u3001\u65b0\u3057\u3044\u30b3\u30f3\u30bb\u30d7\u30c8\u3092\u7d39\u4ecb\u3059\u308b\u30b9\u30bf\u30fc\u30c8\u5730\u70b9\u3060\u304b\u3089\u3067\u3042\u308b\u3002
\n\u524d\u7bc0\u307e\u3067\u306e\u30b3\u30fc\u30c9\u306f\u4ee5\u524d\u306e\u7ae0\u3067\u5341\u5206\u306b\u89e3\u8aac\u3055\u308c\u3066\u3044\u308b\u3002<\/p>\n
\u6211\u3005\u304c\u3084\u308a\u305f\u3044\u4e8b\u3092\u30b3\u30fc\u30c9\u306b\u884c\u308f\u305b\u308b\u305f\u3081\u306b\u3001\u4ee5\u4e0b\u306e\u7c21\u5358\u306a\u4f8b\u3092\u898b\u3066\u3001\u8003\u3048\u3066\u307f\u3088\u3046\u3002<\/p>\n
extern foo();\r\nextern bar();\r\ndef baz(x) if x then foo() else bar();<\/pre>\n
\u3082\u3057\u6700\u9069\u5316\u7121\u3057\u306a\u3089\u3001\u4e0a\u306e\u30b3\u30fc\u30c9\u306f\u4e07\u83ef\u93e1\u306b\u3088\u308a\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u306a\u308b\u306f\u305a\u3067\u3042\u308b\u3002<\/p>\n
declare double @foo()\r\n\r\ndeclare double @bar()\r\n\r\ndefine double @baz(double %x) {\r\nentry:\r\n  %ifcond = fcmp one double %x, 0.000000e+00\r\n  br i1 %ifcond, label %then, label %else\r\n\r\nthen:       ; preds = %entry\r\n  %calltmp = call double @foo()\r\n  br label %ifcont\r\n\r\nelse:       ; preds = %entry\r\n  %calltmp1 = call double @bar()\r\n  br label %ifcont\r\n\r\nifcont:     ; preds = %else, %then\r\n  %iftmp = phi double [ %calltmp, %then ], [ %calltmp1, %else ]\r\n  ret double %iftmp\r\n}<\/pre>\n
\u5236\u5fa1\u30d5\u30ed\u30fc\u30b0\u30e9\u30d5\u3092\u8996\u899a\u5316\u3059\u308b\u305f\u3081\u306b\u3001LLVM\u306e”opt”\u30c4\u30fc\u30eb\u306e\u30a4\u30ab\u30b7\u305f\u6a5f\u80fd\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u304c\u51fa\u6765\u308b\u3002
\n\u4e0a\u8a18\u3092t.ll\u306b\u4fdd\u5b58\u3057\u305f\u3068\u3057\u3066\u3001”llvm-as <  t.ll | opt -analyze -view-cfg\"\u3092\u5b9f\u884c\u3059\u308b\u3068\u3001\u30a6\u30a4\u30f3\u30c9\u30a6\u304c\u7acb\u3061\u4e0a\u304c\u308a\u3001\u6b21\u306e\u3088\u3046\u306a\u30b0\u30e9\u30d5\u304c\u898b\u308c\u308b\u306f\u305a\u3067\u3042\u308b\u3002\n\u8a33\u6ce8: LLVM\u3092\u30bd\u30fc\u30b9\u304b\u3089\u30b3\u30f3\u30d1\u30a4\u30eb\u3057\u3066\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3057\u305f\u3060\u3051\u3067\u4ed6\u306f\u4f55\u3082\u8a2d\u5b9a\u3057\u3066\u306a\u3044Mac\u3067\u306f\u3001\u4e0a\u8a18\u306e\u30b3\u30de\u30f3\u30c9\u3060\u3051\u3067\u306f\u4f55\u306e\u30a6\u30a4\u30f3\u30c9\u30a6\u3082\u958b\u304b\u306a\u304b\u3063\u305f\u304c\u3001\/tmp\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306b.dot\u30d5\u30a1\u30a4\u30eb\u304c\u51fa\u529b\u3055\u308c\u3001\u305d\u308c\u3092Graphviz\u3067\u958b\u304f\u3068\u540c\u3058\u3082\u306e\u304c\u898b\u308c\u305f\u3002<\/em><\/p>\n
\"cfgbaz-cfac13\"<\/a><\/p>\n
\u3053\u306e\u30b0\u30e9\u30d5\u3092\u5f97\u308b\u65b9\u6cd5\u306f\u4ed6\u306b\u3082\u3042\u308b\u3002
\n\u5b9f\u969b\u306e\u30b3\u30fc\u30c9\u306e\u4e2d\u306b\u3001\u201cF->viewCFG()\u201d \u304b \u201cF->viewCFGOnly()\u201d\u306e\u547c\u3073\u51fa\u3057\uff08F\u306fFunction*\uff09\u3092\u8ffd\u52a0\u3057\u3066\u518d\u30b3\u30f3\u30d1\u30a4\u30eb\u3059\u308b\u304b\u3001\u30c7\u30d0\u30c3\u30ac\u3067\u201cF->viewCFG()\u201d \u304b \u201cF->viewCFGOnly()\u201d\u3092\u547c\u3073\u51fa\u3059\u3068\u540c\u3058\u30b0\u30e9\u30d5\u304c\u5f97\u3089\u308c\u308b\u3002
\nLLVM\u306f\u3001\u3044\u308d\u3093\u306a\u30b0\u30e9\u30d5\u3092\u8996\u899a\u5316\u3059\u308b\u305f\u3081\u306e\u7d20\u6674\u3089\u3057\u3044\u6a5f\u80fd\u3092\u305f\u304f\u3055\u3093\u6301\u3063\u3066\u3044\u308b\u3002<\/p>\n
\u751f\u6210\u3055\u308c\u308b\u3079\u304d\u30b3\u30fc\u30c9\u306b\u8a71\u3092\u623b\u3059\u3068\u3001\u305d\u308c\u306f\u6975\u3081\u3066\u30b7\u30f3\u30d7\u30eb\u3067\u3042\u308b\u3002
\nentry\u30d6\u30ed\u30c3\u30af\u306f\u6761\u4ef6\u5f0f\u3092\u8a55\u4fa1\u3057\uff08\u4e0a\u8a18\u306e\u4f8b\u3067\u306fx\u304c\u6761\u4ef6\u5f0f\u3067\u3042\u308b\uff09\u3001\u305d\u306e\u7d50\u679c\u3092”fcmp one”\u547d\u4ee4\uff08”one”\u306f”Ordered and Not Equal”\uff09\u3092\u7528\u3044\u30660.0\u3068\u6bd4\u8f03\u3059\u308b\u3002
\n\u3053\u306e\u5f0f\u306e\u7d50\u679c\u3092\u5143\u306b\u3001\u30b3\u30fc\u30c9\u306f”then”\u304b”else”\u30d6\u30ed\u30c3\u30af\u3078\u30b8\u30e3\u30f3\u30d7\u3059\u308b\u3002
\n\u305d\u308c\u305e\u308c\u306e\u30d6\u30ed\u30c3\u30af\u306ftrue\u3082\u3057\u304f\u306ffalse\u306e\u5834\u5408\u306e\u5f0f\u3092\u542b\u3093\u3067\u3044\u308b\u3002
\n\u8a33\u6ce8: Ordered and Not Equal\u306eOrdered\u306b\u3064\u3044\u3066\u3002
\nOrdered \u306f2\u3064\u306e\u30aa\u30da\u30e9\u30f3\u30c9\u306e\u3046\u3061\u3069\u3061\u3089\u3082QNAN\u3067\u306f\u306a\u3044\u3068\u3044\u3046\u4e8b\u3092\u610f\u5473\u3059\u308b\u3002
\n\uff08QNAN\u3068\u3044\u3046\u306e\u306f\u591a\u5206\u6d6e\u52d5\u5c0f\u6570\u70b9\u6570\u306b\u304a\u3051\u308bQuiet NaN\u306e\u3053\u3068\u304b\u3068\u601d\u308f\u308c\u308b\u3002\uff09
\nOrdered\u304c\u3042\u308b\u3068\u3044\u3046\u3053\u3068\u306fUnordered\u3082\u3042\u308a\u3001\u305d\u3061\u3089\u306f\u7247\u65b9\u306e\u30aa\u30da\u30e9\u30f3\u30c9\u304cQNAN\u304b\u3082\u3057\u308c\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u3092\u610f\u5473\u3059\u308b\u3002
\nfcmp one <ty> <op1> <op2> \u306e\u5834\u5408\uff08Ordered and Not Equal\u306e\u5834\u5408\uff09\u3001\u4e21\u65b9\u306e\u30aa\u30da\u30e9\u30f3\u30c9\u304cQNAN\u3067\u306f\u306a\u304f\u3001\u306a\u304a\u304b\u3064op1\u3068op2\u304c\u7b49\u3057\u304f\u306a\u3044\u3068\u304d\u306btrue\u3092\u8fd4\u3059\u3002
\nfcmp une <ty> <op1> <op2> \u306e\u5834\u5408\uff08Unordered and Not Equal\u306e\u5834\u5408\uff09\u3001\u7247\u65b9\u306e\u30aa\u30da\u30e9\u30f3\u30c9\u304cQNAN\u3001\u3082\u3057\u304f\u306fop1\u3068op2\u304c\u7b49\u3057\u304f\u306a\u3044\u3068\u304d\u306btrue\u3092\u8fd4\u3059\u3002<\/em><\/p>\n
then\/else\u30d6\u30ed\u30c3\u30af\u306e\u5b9f\u884c\u304c\u7d42\u308f\u308c\u3070\u3001\u305d\u308c\u30892\u3064\u306e\u679d\u5206\u304b\u308c\u306f\u3001if\/then\/else\u306e\u5f8c\u306b\u3042\u308b\u30b3\u30fc\u30c9\u3092\u5b9f\u884c\u3059\u308b\u305f\u3081\u306b\u3001ifcont\u30d6\u30ed\u30c3\u30af\u306b\u5408\u6d41\u3059\u308b\u3002
\n\u3053\u306e\u4f8b\u306e\u5834\u5408\u3060\u3068\u3001\u6b8b\u3063\u3066\u308b\u306e\u306f\u95a2\u6570\u306e\u547c\u3073\u51fa\u3057\u5143\u306b\u623b\u308b\u3068\u3044\u3046\u3053\u3068\u3060\u3051\u3067\u3042\u308b\u3002
\n\u3053\u3053\u3067\u7591\u554f\u304c\u601d\u3044\u6d6e\u304b\u3076\u3002
\n\u3069\u3063\u3061\u306e\u5f0f\u306e\u7d50\u679c\u3092\u8fd4\u3059\u304b\u306b\u3064\u3044\u3066\u305d\u306e\u30b3\u30fc\u30c9\u306f\u3069\u3046\u3084\u3063\u3066\u77e5\u308b\u306e\u304b\uff1f<\/p>\n
\u3053\u306e\u7591\u554f\u3078\u306e\u7b54\u3048\u306f\u3001\u91cd\u8981\u306aSSA\u547d\u4ee4\u3067\u3042\u308bphi\u547d\u4ee4\u306b\u95a2\u4fc2\u3059\u308b\u3002
\n\u3082\u3057\u3001SSA\u306b\u95a2\u3057\u3066\u3088\u304f\u77e5\u3089\u306a\u3051\u308c\u3070\u3001Wikipedia\u306e\u8a18\u4e8b\uff08http:\/\/en.wikipedia.org\/wiki\/Static_single_assignment_form<\/a>\uff09\u304c\u826f\u3044\u5c0e\u5165\u306b\u306a\u308b\u3057\u3001SSA\u306b\u5bfe\u3059\u308b\u4ed6\u306e\u69d8\u3005\u306a\u8aac\u660e\u306b\u3064\u3044\u3066\u597d\u304d\u306a\u691c\u7d22\u30a8\u30f3\u30b8\u30f3\u3067\u63a2\u3059\u3053\u3068\u3082\u51fa\u6765\u308b\u3002
\n\u8a33\u6ce8: \u65e5\u672c\u8a9e\u3060\u3068\u9759\u7684\u5358\u4e00\u4ee3\u5165\u3067\u691c\u7d22\u3059\u3079\u3057\u3002<\/em><\/p>\n
\u7c21\u5358\u306b\u8aac\u660e\u3059\u308b\u3068\u3001phi\u547d\u4ee4\u306e\u5b9f\u884c\u306b\u306f\u3001\u5236\u5fa1\u304c\u3069\u306e\u30d6\u30ed\u30c3\u30af\u304b\u3089\u6765\u305f\u306e\u304b\u899a\u3048\u3066\u304a\u304f\u4e8b\u304c\u5fc5\u8981\u3068\u306a\u308b\u3002
\nphi\u547d\u4ee4\u306f\u3001\u5165\u3063\u3066\u304d\u305f\u5236\u5fa1\u30d6\u30ed\u30c3\u30af\u306b\u5408\u81f4\u3059\u308b\u5024\u3092\u53d7\u3051\u53d6\u308b\u3002
\n\u3053\u306e\u5834\u5408\u3001\u5236\u5fa1\u304c”then”\u30d6\u30ed\u30c3\u30af\u304b\u3089\u6765\u305f\u5834\u5408\u3001phi\u547d\u4ee4\u306fcalltmp\u306e\u5024\u3092\u53d7\u3051\u53d6\u308b\u3002
\n\u3082\u3057\u5236\u5fa1\u304c”else”\u30d6\u30ed\u30c3\u30af\u304b\u3089\u6765\u305f\u5834\u5408\u3001phi\u547d\u4ee4\u306fcalltmp1\u306e\u5024\u3092\u53d7\u3051\u53d6\u308b\u3002<\/p>\n
\u3053\u306e\u6642\u70b9\u3067\u3001\u3042\u306a\u305f\u306f\u591a\u5206\u3053\u3046\u8003\u3048\u59cb\u3081\u308b\u3060\u308d\u3046\u3002
\n\u300c\u306a\u3093\u3066\u3053\u3063\u305f\uff01LLVM\u3092\u4f7f\u7528\u3059\u308b\u305f\u3081\u306b\u3001\u30aa\u30ec\u306e\u30b7\u30f3\u30d7\u30eb\u3067\u30a8\u30ec\u30ac\u30f3\u30c8\u306a\u30d5\u30ed\u30f3\u30c8\u30a8\u30f3\u30c9\u3092\u3001SSA\u5f62\u5f0f\u3092\u751f\u6210\u3059\u308b\u3088\u3046\u306b\u3057\u306a\u304d\u3083\u3044\u3051\u306a\u3044\u3063\u3066\u3053\u3068\u304b\uff01\u300d
\n\u5e78\u904b\u306b\u3082\u305d\u3046\u3067\u306f\u306a\u3044\u3002
\n\u3082\u306e\u51c4\u304f\u91cd\u8981\u306a\u7406\u7531\u304c\u7121\u3044\u9650\u308a\u3001SSA\u69cb\u7bc9\u306e\u30a2\u30eb\u30b4\u30ea\u30ba\u30e0\u3092\u30d5\u30ed\u30f3\u30c8\u30a8\u30f3\u30c9\u306b\u5b9f\u88c5\u3059\u3079\u304d\u3067\u306f\u306a\u3044\u3068\u3001\u6211\u3005\u306f\u5f37\u304f\u30a2\u30c9\u30d0\u30a4\u30b9\u3059\u308b\u3002
\n\u5b9f\u969b\u554f\u984c\u3068\u3057\u3066\u3001\u5e73\u5747\u7684\u306a\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u8a00\u8a9e\u306e\u305f\u3081\u306b\u66f8\u304b\u308c\u305f\u30b3\u30fc\u30c9\u306e\u307e\u308f\u308a\u3067\u6d6e\u304b\u3093\u3067\u3044\u308b\u3001phi\u30ce\u30fc\u30c9\u3092\u5fc5\u8981\u3068\u3059\u308b\u304b\u3082\u3057\u308c\u306a\u30442\u7a2e\u985e\u306e\u5024\u304c\u3042\u308b\u3002
\n\uff08In practice, there are two sorts of values that float around in code written for your average imperative programming language that might need Phi nodes:\uff09<\/p>\n
1. \u30e6\u30fc\u30b6\u5909\u6570\u3092\u307e\u304d\u3053\u3080\u30b3\u30fc\u30c9\u3002x = 1; x = x + 1;
\n2. \u3053\u306e\u5834\u5408\u306ephi\u30ce\u30fc\u30c9\u306e\u3088\u3046\u306a\u3001AST\u306e\u69cb\u9020\u4e0a\u6697\u9ed9\u7684\u306b\u5b58\u5728\u3059\u308b\u5024\u3002<\/p>\n
\u3053\u306e\u30c1\u30e5\u30fc\u30c8\u30ea\u30a2\u30eb\u306e\u7b2c7\u7ae0\uff08\u5909\u66f4\u53ef\u80fd\u306a\u5909\u6570\uff09\u3067\u306f\u30011\u306b\u3064\u3044\u3066\u6df1\u304f\u8aac\u660e\u3059\u308b\u3002
\n\u3053\u306e\u3088\u3046\u306a\u5834\u5408\u3092\u5236\u5fa1\u3059\u308b\u305f\u3081\u306bSSA\u3092\u69cb\u7bc9\u3059\u308b\u5fc5\u8981\u304c\u306a\u3044\u3001\u3068\u3044\u3046\u3053\u3068\u3092\u4eca\u306f\u5358\u306b\u4fe1\u3058\u3066\u6b32\u3057\u3044\u3002
\n2\u306b\u3064\u3044\u3066\u306f\u30011\u3068\u540c\u3058\u304f\u7b2c7\u7ae0\u3067\u8aac\u660e\u3059\u308b\u6280\u6cd5\u304b\u3092\u4f7f\u3046\u304b\u3001\u7c21\u5358\u306bphi\u30ce\u30fc\u30c9\u3092\u76f4\u63a5\u633f\u5165\u3059\u308b\u65b9\u6cd5\u304c\u9078\u3079\u308b\u3002
\n\u3053\u306e\u5834\u5408\u3001phi\u30ce\u30fc\u30c9\u3092\u751f\u6210\u3059\u308b\u306e\u306f\u5b9f\u306b\u7c21\u5358\u306a\u306e\u3067\u3001\u6211\u3005\u306f\u76f4\u63a5\u633f\u5165\u3059\u308b\u65b9\u6cd5\u3092\u9078\u629e\u3059\u308b\u3002<\/p>\n
\u3088\u3057\u3001\u5341\u5206\u306a\u52d5\u6a5f\u3068\u6982\u89b3\u3092\u5f97\u305f\u3068\u3053\u308d\u3067\u3001\u30b3\u30fc\u30c9\u3092\u751f\u6210\u3057\u3088\u3046\uff01<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[466,467],"class_list":["post-2973","post","type-post","status-publish","format-standard","hentry","category-tech","tag-kaleidoscope","tag-llvm"],"_links":{"self":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/2973","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/comments?post=2973"}],"version-history":[{"count":0,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/2973\/revisions"}],"wp:attachment":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/media?parent=2973"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/categories?post=2973"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/tags?post=2973"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}