[llvm] 3db6783 - Check result of emitStrLen before passing it to CreateGEP

[Dimitry Andric via llvm-commits]

Author: Dimitry Andric
Date: 2019-11-14T08:04:36+01:00
New Revision: 3db6783d8a7da05a5949bb18e6c8809306c9d0de

URL: https://github.com/llvm/llvm-project/commit/3db6783d8a7da05a5949bb18e6c8809306c9d0de
DIFF: https://github.com/llvm/llvm-project/commit/3db6783d8a7da05a5949bb18e6c8809306c9d0de.diff

LOG: Check result of emitStrLen before passing it to CreateGEP

Summary:
This fixes PR43081, where the transformation of `strchr(p, 0) -> p +
strlen(p)` can cause a segfault, if `-fno-builtin-strlen` is used.  In
that case, `emitStrLen` returns nullptr, which CreateGEP is not designed
to handle.  Also add the minimized code from the PR as a test case.

Reviewers: xbolva00, spatel, jdoerfert, efriedma

Reviewed By: efriedma

Subscribers: lebedev.ri, hiraditya, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D70143

Added: 
    llvm/test/Transforms/InstCombine/pr43081.ll

Modified: 
    llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 0324993a8203..18a17119b47f 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -364,8 +364,8 @@ Value *LibCallSimplifier::optimizeStrChr(CallInst *CI, IRBuilder<> &B) {
   StringRef Str;
   if (!getConstantStringInfo(SrcStr, Str)) {
     if (CharC->isZero()) // strchr(p, 0) -> p + strlen(p)
-      return B.CreateGEP(B.getInt8Ty(), SrcStr, emitStrLen(SrcStr, B, DL, TLI),
-                         "strchr");
+      if (Value *StrLen = emitStrLen(SrcStr, B, DL, TLI))
+        return B.CreateGEP(B.getInt8Ty(), SrcStr, StrLen, "strchr");
     return nullptr;
   }
 

diff  --git a/llvm/test/Transforms/InstCombine/pr43081.ll b/llvm/test/Transforms/InstCombine/pr43081.ll
new file mode 100644
index 000000000000..42f910043dba
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/pr43081.ll
@@ -0,0 +1,15 @@
+; RUN: opt < %s -instcombine -disable-builtin strlen -S | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+declare i8* @strchr(i8*, i32)
+
+define i8* @pr43081(i8* %a) {
+entry:
+  %a.addr = alloca i8*, align 8
+  store i8* %a, i8** %a.addr, align 8
+  %0 = load i8*, i8** %a.addr, align 8
+  %call = call i8* @strchr(i8* %0, i32 0)
+  ret i8* %call
+; CHECK: call i8* @strchr
+}