[PATCH] D13301: [SimplifyLibCalls] Fix instruction misplacement in string/memory libcall optimization

[Bruno Cardoso Lopes via llvm-commits]

bruno created this revision.
bruno added reviewers: ab, echristo.
bruno added a subscriber: llvm-commits.
bruno set the repository for this revision to rL LLVM.

    When trying to optimize fortified library functions use the right
    location to insert new instructions in order to preserve correct
    def-use order.
    
    This fixes an issue where a misplaced instruction definition would
    happen to be *after* one of its use after a RAUW, forming invalid IR.
    This behaviour was introduced by r227250.

Repository:
  rL LLVM

http://reviews.llvm.org/D13301

Files:
  lib/Transforms/Utils/SimplifyLibCalls.cpp
  test/Transforms/InstCombine/memset_chk-1.ll

Index: test/Transforms/InstCombine/memset_chk-1.ll
===================================================================
--- test/Transforms/InstCombine/memset_chk-1.ll
+++ test/Transforms/InstCombine/memset_chk-1.ll
@@ -63,4 +63,30 @@
   ret i8* %ret
 }
 
+; Test that RAUW in SimplifyLibCalls for __memset_chk generates valid IR
+define i32 @test_rauw(i8* %a, i8* %b, i8** %c) {
+; CHECK-LABEL: test_rauw
+entry:
+  %call49 = call i64 @strlen(i8* %a)
+  %add180 = add i64 %call49, 1
+  %yo107 = call i64 @llvm.objectsize.i64.p0i8(i8* %b, i1 false)
+  %call50 = call i8* @__memmove_chk(i8* %b, i8* %a, i64 %add180, i64 %yo107)
+; CHECK: %strlen = call i64 @strlen(i8* %b)
+; CHECK-NEXT: %strchr2 = getelementptr i8, i8* %b, i64 %strlen
+  %call51i = call i8* @strrchr(i8* %b, i32 0)
+  %d = load i8*, i8** %c, align 8
+  %sub182 = ptrtoint i8* %d to i64
+  %sub183 = ptrtoint i8* %b to i64
+  %sub184 = sub i64 %sub182, %sub183
+  %add52.i.i = add nsw i64 %sub184, 1
+; CHECK: call void @llvm.memset.p0i8.i64(i8* %strchr2
+  %call185 = call i8* @__memset_chk(i8* %call51i, i32 0, i64 %add52.i.i, i64 -1)
+  ret i32 4
+}
+
+declare i8* @__memmove_chk(i8*, i8*, i64, i64)
+declare i8* @strrchr(i8*, i32)
+declare i64 @strlen(i8* nocapture)
+declare i64 @llvm.objectsize.i64.p0i8(i8*, i1)
+
 declare i8* @__memset_chk(i8*, i32, i64, i64)
Index: lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -2075,8 +2075,11 @@
   if (Value *SimplifiedFortifiedCI = FortifiedSimplifier.optimizeCall(CI)) {
     // Try to further simplify the result.
     CallInst *SimplifiedCI = dyn_cast<CallInst>(SimplifiedFortifiedCI);
+    // Use an IR Builder from SimplifiedCI if available instead of CI
+    // to guarantee we reach all uses we might replace later on.
+    IRBuilder<> TmpBuilder(SimplifiedCI ? SimplifiedCI : CI);
     if (SimplifiedCI && SimplifiedCI->getCalledFunction())
-      if (Value *V = optimizeStringMemoryLibCall(SimplifiedCI, Builder)) {
+      if (Value *V = optimizeStringMemoryLibCall(SimplifiedCI, TmpBuilder)) {
         // If we were able to further simplify, remove the now redundant call.
         SimplifiedCI->replaceAllUsesWith(V);
         SimplifiedCI->eraseFromParent();


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D13301.36132.patch
Type: text/x-patch
Size: 2344 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150930/657fa45e/attachment-0001.bin>