[llvm] 34ab569 - Support zero size types in StackSafetyAnalysis.

[Evgenii Stepanov via llvm-commits]

Author: Evgenii Stepanov
Date: 2020-01-27T15:22:59-08:00
New Revision: 34ab56904e303c6bbe77f4232341b73dd0f2443d

URL: https://github.com/llvm/llvm-project/commit/34ab56904e303c6bbe77f4232341b73dd0f2443d
DIFF: https://github.com/llvm/llvm-project/commit/34ab56904e303c6bbe77f4232341b73dd0f2443d.diff

LOG: Support zero size types in StackSafetyAnalysis.

Reviewers: vitalybuka

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73395

Added: 
    

Modified: 
    llvm/lib/Analysis/StackSafetyAnalysis.cpp
    llvm/test/Analysis/StackSafetyAnalysis/local.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/StackSafetyAnalysis.cpp b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
index d85da765b7fe..33a326e4a86f 100644
--- a/llvm/lib/Analysis/StackSafetyAnalysis.cpp
+++ b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
@@ -252,6 +252,10 @@ StackSafetyLocalAnalysis::offsetFromAlloca(Value *Addr,
 ConstantRange
 StackSafetyLocalAnalysis::getAccessRange(Value *Addr, const Value *AllocaPtr,
                                          ConstantRange SizeRange) {
+  // Zero-size loads and stores do not access memory.
+  if (SizeRange.isEmptySet())
+    return ConstantRange::getEmpty(PointerSize);
+
   if (!SE.isSCEVable(Addr->getType()))
     return UnknownRange;
 

diff  --git a/llvm/test/Analysis/StackSafetyAnalysis/local.ll b/llvm/test/Analysis/StackSafetyAnalysis/local.ll
index b751297644c8..0ba1694e99eb 100644
--- a/llvm/test/Analysis/StackSafetyAnalysis/local.ll
+++ b/llvm/test/Analysis/StackSafetyAnalysis/local.ll
@@ -368,3 +368,20 @@ entry:
   store <vscale x 4 x i32> %v, <vscale x 4 x i32>* %p, align 4
   ret void
 }
+
+%zerosize_type = type {}
+
+define void @ZeroSize(%zerosize_type *%p)  {
+; CHECK-LABEL: @ZeroSize dso_preemptable{{$}}
+; CHECK-NEXT: args uses:
+; CHECK-NEXT:   p[]: empty-set
+; CHECK-NEXT: allocas uses:
+; CHECK-NEXT:   x[0]: empty-set
+; CHECK-NOT: ]:
+entry:
+  %x = alloca %zerosize_type, align 4
+  store %zerosize_type undef, %zerosize_type* %x, align 4
+  store %zerosize_type undef, %zerosize_type* undef, align 4
+  %val = load %zerosize_type, %zerosize_type* %p, align 4
+  ret void
+}