dnrops
/
clang
mirror of https://github.com/microsoft/clang.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Patch to fix pragma metadata for do-while loops 

Summary:
Make sure that loop metadata only is put on the backedge
when expanding a do-while loop.
Previously we added the loop metadata also on the branch
in the pre-header. That could confuse optimization passes
and result in the loop metadata being associated with the
wrong loop.

Fixes https://bugs.llvm.org/show_bug.cgi?id=38011

Committing on behalf of deepak2427 (Deepak Panickal)

Reviewers: #clang, ABataev, hfinkel, aaron.ballman, bjope

Reviewed By: bjope

Subscribers: bjope, rsmith, shenhan, zzheng, xbolva00, lebedev.ri, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D48721

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@336717 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bjorn Pettersson 2018-07-10 19:55:02 +00:00
parent 8430288c27
commit 8275ce24a4
2 changed files with 41 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
lib/CodeGen/CGStmt.cpp
View File

@ -777,11 +777,6 @@ void CodeGenFunction::EmitDoStmt(const DoStmt &S,
// Emit the body of the loop. // Emit the body of the loop.
llvm::BasicBlock *LoopBody = createBasicBlock("do.body"); llvm::BasicBlock *LoopBody = createBasicBlock("do.body");
const SourceRange &R = S.getSourceRange();
LoopStack.push(LoopBody, CGM.getContext(), DoAttrs,
SourceLocToDebugLoc(R.getBegin()),
SourceLocToDebugLoc(R.getEnd()));
EmitBlockWithFallThrough(LoopBody, &S); EmitBlockWithFallThrough(LoopBody, &S);
{ {
RunCleanupsScope BodyScope(*this); RunCleanupsScope BodyScope(*this);
@ -790,6 +785,11 @@ void CodeGenFunction::EmitDoStmt(const DoStmt &S,
EmitBlock(LoopCond.getBlock()); EmitBlock(LoopCond.getBlock());
const SourceRange &R = S.getSourceRange();
LoopStack.push(LoopBody, CGM.getContext(), DoAttrs,
SourceLocToDebugLoc(R.getBegin()),
SourceLocToDebugLoc(R.getEnd()));
// C99 6.8.5.2: "The evaluation of the controlling expression takes place // C99 6.8.5.2: "The evaluation of the controlling expression takes place
// after each execution of the loop body." // after each execution of the loop body."

36
test/CodeGen/pragma-do-while.cpp Normal file
View File

@ -0,0 +1,36 @@
// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s
// We expect to get a loop structure like this:
// do.body: ; preds = %do.cond, ...
// ...
// br label %do.cond
// do.cond: ; preds = %do.body
// ...
// br i1 %cmp, label %do.body, label %do.end
// do.end: ; preds = %do.cond
// ...
//
// Verify that the loop metadata only is put on the backedge.
//
// CHECK-NOT: llvm.loop
// CHECK-LABEL: do.cond:
// CHECK: br {{.*}}, label %do.body, label %do.end, !llvm.loop ![[LMD1:[0-9]+]]
// CHECK-LABEL: do.end:
// CHECK-NOT: llvm.loop
// CHECK: ![[LMD1]] = distinct !{![[LMD1]], ![[LMD2:[0-9]+]]}
// CHECK: ![[LMD2]] = !{!"llvm.loop.unroll.count", i32 4}
int test(int a[], int n) {
int i = 0;
int sum = 0;
#pragma unroll 4
do
{
a[i] = a[i] + 1;
sum = sum + a[i];
i++;
} while (i < n);
return sum;
}