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InstCombine: Preserve nuw when reassociating nuw ops [1/3] 

Alive says this is OK.

llvm-svn: 364233
This commit is contained in:
Matt Arsenault 2019-06-24 21:36:59 +00:00
parent 1e5116cbb3
commit 5a89ba7343
3 changed files with 19 additions and 9 deletions
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18
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -223,6 +223,11 @@ static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) {
return !Overflow;
}
static bool hasNoUnsignedWrap(BinaryOperator &I) {
OverflowingBinaryOperator *OBO = dyn_cast<OverflowingBinaryOperator>(&I);
return OBO && OBO->hasNoUnsignedWrap();
}
/// Conservatively clears subclassOptionalData after a reassociation or
/// commutation. We preserve fast-math flags when applicable as they can be
/// preserved.
@ -329,14 +334,19 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
I.setOperand(1, V);
// Conservatively clear the optional flags, since they may not be
// preserved by the reassociation.
if (MaintainNoSignedWrap(I, B, C) &&
bool IsNUW = hasNoUnsignedWrap(I) && hasNoUnsignedWrap(*Op0);
bool IsNSW = MaintainNoSignedWrap(I, B, C);
ClearSubclassDataAfterReassociation(I);
if (IsNUW)
I.setHasNoUnsignedWrap(true);
if (IsNSW &&
(!Op0 || (isa<BinaryOperator>(Op0) && Op0->hasNoSignedWrap()))) {
// Note: this is only valid because SimplifyBinOp doesn't look at
// the operands to Op0.
I.clearSubclassOptionalData();
I.setHasNoSignedWrap(true);
} else {
ClearSubclassDataAfterReassociation(I);
}
Changed = true;

2
llvm/test/Transforms/InstCombine/reassociate-nuw.ll
View File

@ -3,7 +3,7 @@
define i32 @reassoc_add_nuw(i32 %x) {
; CHECK-LABEL: @reassoc_add_nuw(
; CHECK-NEXT: [[ADD1:%.*]] = add i32 [[X:%.*]], 68
; CHECK-NEXT: [[ADD1:%.*]] = add nuw i32 [[X:%.*]], 68
; CHECK-NEXT: ret i32 [[ADD1]]
;
%add0 = add nuw i32 %x, 4

8
llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
View File

@ -172,7 +172,7 @@ define void @test3(i64 %trip, i64 %add) {
; PROLOG: loop_exiting_bb1.7:
; PROLOG-NEXT: switch i64 %sum.next.6, label %loop_latch.7
; PROLOG: loop_latch.7:
; PROLOG-NEXT: %iv_next.7 = add nsw i64 %iv, 8
; PROLOG-NEXT: %iv_next.7 = add nuw nsw i64 %iv, 8
; PROLOG-NEXT: %sum.next.7 = add i64 %sum.next.6, %add
; PROLOG-NEXT: %cmp.7 = icmp eq i64 %iv_next.7, %trip
; PROLOG-NEXT: br i1 %cmp.7, label %exit2.loopexit.unr-lcssa, label %loop_header
@ -426,7 +426,7 @@ define i64 @test5(i64 %trip, i64 %add, i1 %cond) {
; PROLOG-NEXT: %result = phi i64 [ %result.ph, %exit1.loopexit ], [ %ivy.prol, %exit1.loopexit1 ]
; PROLOG-NEXT: ret i64 %result
; PROLOG: loop_latch.7:
; PROLOG: %iv_next.7 = add nsw i64 %iv, 8
; PROLOG: %iv_next.7 = add nuw nsw i64 %iv, 8
entry:
br label %loop_header
@ -560,7 +560,7 @@ loopexit1: ; preds = %header
}
; Nested loop and inner loop is unrolled
; FIXME: we cannot unroll with epilog remainder currently, because
; FIXME: we cannot unroll with epilog remainder currently, because
; the outer loop does not contain the epilog preheader and epilog exit (while
; infact it should). This causes us to choke up on LCSSA form being incorrect in
; outer loop. However, the exit block where LCSSA fails, is infact still within
@ -578,7 +578,7 @@ define void @test8() {
; PROLOG: %lcmp.mod = icmp eq i64
; PROLOG-NEXT: br i1 %lcmp.mod, label %innerH.prol.loopexit, label %innerH.prol.preheader
; PROLOG: latch.6:
; PROLOG-NEXT: %tmp4.7 = add nsw i64 %tmp3, 8
; PROLOG-NEXT: %tmp4.7 = add nuw nsw i64 %tmp3, 8
; PROLOG-NEXT: br i1 false, label %outerloop.loopexit.loopexit, label %latch.7
; PROLOG: latch.7
; PROLOG-NEXT: %tmp6.7 = icmp ult i64 %tmp4.7, 100