[llvm] r364155 - [IndVars] Remove dead instructions after folding trivial loop exit
Philip Reames via llvm-commits
llvm-commits at lists.llvm.org
Sun Jun 23 10:06:57 PDT 2019
Author: reames
Date: Sun Jun 23 10:06:57 2019
New Revision: 364155
URL: http://llvm.org/viewvc/llvm-project?rev=364155&view=rev
Log:
[IndVars] Remove dead instructions after folding trivial loop exit
In rL364135, I taught IndVars to fold exiting branches in loops with a zero backedge taken count (i.e. loops that only run one iteration). This extends that to eliminate the dead comparison left around.
Modified:
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll
llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll
llvm/trunk/test/Transforms/IndVarSimplify/floating-point-iv.ll
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=364155&r1=364154&r2=364155&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Sun Jun 23 10:06:57 2019
@@ -2732,10 +2732,12 @@ bool IndVarSimplify::run(Loop *L) {
if (ExitCount->isZero()) {
auto *BI = cast<BranchInst>(ExitingBB->getTerminator());
bool ExitIfTrue = !L->contains(*succ_begin(ExitingBB));
- auto *NewCond = ExitIfTrue ?
- ConstantInt::getTrue(BI->getCondition()->getType()) :
- ConstantInt::getFalse(BI->getCondition()->getType());
+ auto *OldCond = BI->getCondition();
+ auto *NewCond = ExitIfTrue ? ConstantInt::getTrue(OldCond->getType()) :
+ ConstantInt::getFalse(OldCond->getType());
BI->setCondition(NewCond);
+ if (OldCond->use_empty())
+ DeadInsts.push_back(OldCond);
Changed = true;
continue;
}
Modified: llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll?rev=364155&r1=364154&r2=364155&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll Sun Jun 23 10:06:57 2019
@@ -276,14 +276,8 @@ define i32 @func_12() nounwind uwtable {
; CHECK-NEXT: tail call void @llvm.trap()
; CHECK-NEXT: unreachable
; CHECK: forcond38:
-; CHECK-NEXT: [[__KEY8_0:%.*]] = phi i32 [ [[TMP81:%.*]], [[NOASSERT68:%.*]] ], [ 2, [[FORCOND38_PREHEADER]] ]
-; CHECK-NEXT: br i1 true, label [[NOASSERT68]], label [[UNROLLEDEND:%.*]]
+; CHECK-NEXT: br i1 true, label [[NOASSERT68:%.*]], label [[UNROLLEDEND:%.*]]
; CHECK: noassert68:
-; CHECK-NEXT: [[TMP57:%.*]] = sdiv i32 -32768, [[__KEY8_0]]
-; CHECK-NEXT: [[SEXT34:%.*]] = shl i32 [[TMP57]], 16
-; CHECK-NEXT: [[SEXT21:%.*]] = shl i32 [[TMP57]], 16
-; CHECK-NEXT: [[TMP76:%.*]] = icmp ne i32 [[SEXT34]], [[SEXT21]]
-; CHECK-NEXT: [[TMP81]] = add nuw nsw i32 [[__KEY8_0]], 1
; CHECK-NEXT: br i1 false, label [[FORCOND38]], label [[ASSERT77:%.*]]
; CHECK: assert77:
; CHECK-NEXT: tail call void @llvm.trap()
Modified: llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll?rev=364155&r1=364154&r2=364155&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll Sun Jun 23 10:06:57 2019
@@ -170,10 +170,6 @@ define void @test_06(i32 %n) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
-; CHECK-NEXT: [[IV:%.*]] = phi i64 [ -2147483649, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
-; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
-; CHECK-NEXT: [[NARROW_IV:%.*]] = trunc i64 [[IV]] to i32
-; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[NARROW_IV]], [[N:%.*]]
; CHECK-NEXT: br i1 false, label [[LOOP]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void
@@ -350,10 +346,6 @@ define void @test_06_unsigned(i32 %n) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
-; CHECK-NEXT: [[IV:%.*]] = phi i64 [ -1, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
-; CHECK-NEXT: [[IV_NEXT]] = add nsw i64 [[IV]], 1
-; CHECK-NEXT: [[NARROW_IV:%.*]] = trunc i64 [[IV]] to i32
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[NARROW_IV]], [[N:%.*]]
; CHECK-NEXT: br i1 false, label [[LOOP]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void
Modified: llvm/trunk/test/Transforms/IndVarSimplify/floating-point-iv.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/floating-point-iv.ll?rev=364155&r1=364154&r2=364155&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/floating-point-iv.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/floating-point-iv.ll Sun Jun 23 10:06:57 2019
@@ -50,7 +50,7 @@ bb: ; preds = %bb, %entry
return:
ret void
; CHECK-LABEL: @test3(
-; CHECK: fcmp
+; CHECK: br i1 false
}
define void @test4() nounwind {
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