http://llvm.org/bugs/show_bug.cgi?id=10484
Summary: Lifetime markers are preventing alloca promotion
Product: libraries
Version: trunk
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Created an attachment (id=6929)
--> (http://llvm.org/bugs/attachment.cgi?id=6929)
Unoptimized bitcode for clang's Stmp.cpp
The llvm.lifetime markers inserted by the inliner are preventing allocas from
being promoted to registers.
This causes some functions to use a lot more stack space.
The attached example is from clang's own Stmt.cpp. The function
_ZNK5clang4Stmt14getSourceRangeEv has more then 50 allocas after optimizing to
file with 'opt -O2". If I apply this patch:
diff --git a/lib/Transforms/Utils/InlineFunction.cpp
b/lib/Transforms/Utils/InlineFunction.cpp
index 714b12c..c613d1a 100644
--- a/lib/Transforms/Utils/InlineFunction.cpp
+++ b/lib/Transforms/Utils/InlineFunction.cpp
@@ -934,7 +934,7 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo
&IFI) {
// Leave lifetime markers for the static alloca's, scoping them to the
// function we just inlined.
- if (!IFI.StaticAllocas.empty()) {
+ if (0 && !IFI.StaticAllocas.empty()) {
IRBuilder<> builder(FirstNewBlock->begin());
for (unsigned ai = 0, ae = IFI.StaticAllocas.size(); ai != ae; ++ai) {
AllocaInst *AI = IFI.StaticAllocas[ai];
All of those allocas are optimized away.
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