From 3e7ee5428d3442564b9581adc2fb14f4e0a54bcd Mon Sep 17 00:00:00 2001 From: Florian Hahn Date: Thu, 15 Apr 2021 22:52:22 +0100 Subject: [PATCH] [InferAttrs] Do not mark first argument of str(n)cat as writeonly. str(n)cat appends a copy of the second argument to the end of the first argument. To find the end of the first argument, str(n)cat has to read from it until it finds the terminating 0. So it should not be marked as writeonly. I think this means the argument should not be marked as writeonly. (This is causing a mis-compile with legacy DSE, before it got removed) Reviewed By: efriedma Differential Revision: https://reviews.llvm.org/D100601 --- llvm/lib/Transforms/Utils/BuildLibCalls.cpp | 12 ++++++++++-- llvm/test/Transforms/InferFunctionAttrs/annotate.ll | 4 ++-- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp index cfb8c0636043..33740eaee0fb 100644 --- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp +++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp @@ -257,11 +257,19 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) { Changed |= setDoesNotCapture(F, 1); Changed |= setOnlyReadsMemory(F, 0); return Changed; - case LibFunc_strcpy: - case LibFunc_strncpy: case LibFunc_strcat: case LibFunc_strncat: + Changed |= setOnlyAccessesArgMemory(F); + Changed |= setDoesNotThrow(F); Changed |= setWillReturn(F); + Changed |= setReturnedArg(F, 0); + Changed |= setDoesNotCapture(F, 1); + Changed |= setOnlyReadsMemory(F, 1); + Changed |= setDoesNotAlias(F, 0); + Changed |= setDoesNotAlias(F, 1); + return Changed; + case LibFunc_strcpy: + case LibFunc_strncpy: Changed |= setReturnedArg(F, 0); LLVM_FALLTHROUGH; case LibFunc_stpcpy: diff --git a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll index 05cf79b3874b..d6e8c5b51c1a 100644 --- a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll +++ b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll @@ -839,7 +839,7 @@ declare i8* @stpncpy(i8*, i8*, i64) ; CHECK: declare i32 @strcasecmp(i8* nocapture, i8* nocapture) [[NOFREE_NOUNWIND_READONLY_WILLRETURN:#[0-9]+]] declare i32 @strcasecmp(i8*, i8*) -; CHECK: declare i8* @strcat(i8* noalias returned writeonly, i8* noalias nocapture readonly) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] +; CHECK: declare i8* @strcat(i8* noalias returned, i8* noalias nocapture readonly) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] declare i8* @strcat(i8*, i8*) ; CHECK: declare i8* @strchr(i8*, i32) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY]] @@ -866,7 +866,7 @@ declare i64 @strlen(i8*) ; CHECK: declare i32 @strncasecmp(i8* nocapture, i8* nocapture, i64) [[NOFREE_NOUNWIND_READONLY_WILLRETURN]] declare i32 @strncasecmp(i8*, i8*, i64) -; CHECK: declare i8* @strncat(i8* noalias returned writeonly, i8* noalias nocapture readonly, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] +; CHECK: declare i8* @strncat(i8* noalias returned, i8* noalias nocapture readonly, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] declare i8* @strncat(i8*, i8*, i64) ; CHECK: declare i32 @strncmp(i8* nocapture, i8* nocapture, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY]]