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[InstSimplify] simplify abs if operand is known non-negative

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abs() should be rare enough that using value tracking is not going
to be a compile-time cost burden, so use it to reduce a variety of
potential patterns. We do this in DAGCombiner too.

Differential Revision: https://reviews.llvm.org/D85043
This commit is contained in:
Sanjay Patel 2020-08-01 07:46:23 -04:00
parent 5c3a911802
commit afc3df8955
2 changed files with 12 additions and 11 deletions
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6
lib/Analysis/InstructionSimplify.cpp
View File

@ -5255,6 +5255,12 @@ static Value *simplifyBinaryIntrinsic(Function *F, Value *Op0, Value *Op1,
Type *ReturnType = F->getReturnType();
unsigned BitWidth = ReturnType->getScalarSizeInBits();
switch (IID) {
case Intrinsic::abs:
// If the sign bit is clear already, then abs does not do anything.
if (isKnownNonNegative(Op0, Q.DL, 0, Q.AC, Q.CxtI, Q.DT))
return Op0;
break;
case Intrinsic::smax:
case Intrinsic::smin:
case Intrinsic::umax:

17
test/Transforms/InstSimplify/call.ll
View File

@ -5,13 +5,12 @@
declare i32 @llvm.abs.i32(i32, i1)
declare <3 x i82> @llvm.abs.v3i82(<3 x i82>, i1)
; TODO: If the sign bit is known zero, the abs is not needed.
; If the sign bit is known zero, the abs is not needed.
define i32 @zext_abs(i31 %x) {
; CHECK-LABEL: @zext_abs(
; CHECK-NEXT: [[ZEXT:%.*]] = zext i31 [[X:%.*]] to i32
; CHECK-NEXT: [[ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[ZEXT]], i1 false)
; CHECK-NEXT: ret i32 [[ABS]]
; CHECK-NEXT: ret i32 [[ZEXT]]
;
%zext = zext i31 %x to i32
%abs = call i32 @llvm.abs.i32(i32 %zext, i1 false)
@ -21,8 +20,7 @@ define i32 @zext_abs(i31 %x) {
define <3 x i82> @lshr_abs(<3 x i82> %x) {
; CHECK-LABEL: @lshr_abs(
; CHECK-NEXT: [[LSHR:%.*]] = lshr <3 x i82> [[X:%.*]], <i82 1, i82 1, i82 1>
; CHECK-NEXT: [[ABS:%.*]] = call <3 x i82> @llvm.abs.v3i82(<3 x i82> [[LSHR]], i1 true)
; CHECK-NEXT: ret <3 x i82> [[ABS]]
; CHECK-NEXT: ret <3 x i82> [[LSHR]]
;
%lshr = lshr <3 x i82> %x, <i82 1, i82 1, i82 1>
%abs = call <3 x i82> @llvm.abs.v3i82(<3 x i82> %lshr, i1 true)
@ -32,8 +30,7 @@ define <3 x i82> @lshr_abs(<3 x i82> %x) {
define i32 @and_abs(i32 %x) {
; CHECK-LABEL: @and_abs(
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X:%.*]], 2147483644
; CHECK-NEXT: [[ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[AND]], i1 true)
; CHECK-NEXT: ret i32 [[ABS]]
; CHECK-NEXT: ret i32 [[AND]]
;
%and = and i32 %x, 2147483644
%abs = call i32 @llvm.abs.i32(i32 %and, i1 true)
@ -43,8 +40,7 @@ define i32 @and_abs(i32 %x) {
define <3 x i82> @select_abs(<3 x i1> %cond) {
; CHECK-LABEL: @select_abs(
; CHECK-NEXT: [[SEL:%.*]] = select <3 x i1> [[COND:%.*]], <3 x i82> zeroinitializer, <3 x i82> <i82 2147483647, i82 42, i82 1>
; CHECK-NEXT: [[ABS:%.*]] = call <3 x i82> @llvm.abs.v3i82(<3 x i82> [[SEL]], i1 false)
; CHECK-NEXT: ret <3 x i82> [[ABS]]
; CHECK-NEXT: ret <3 x i82> [[SEL]]
;
%sel = select <3 x i1> %cond, <3 x i82> zeroinitializer, <3 x i82> <i82 2147483647, i82 42, i82 1>
%abs = call <3 x i82> @llvm.abs.v3i82(<3 x i82> %sel, i1 false)
@ -57,8 +53,7 @@ define i32 @assume_abs(i32 %x) {
; CHECK-LABEL: @assume_abs(
; CHECK-NEXT: [[ASSUME:%.*]] = icmp sge i32 [[X:%.*]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[ASSUME]])
; CHECK-NEXT: [[ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[X]], i1 true)
; CHECK-NEXT: ret i32 [[ABS]]
; CHECK-NEXT: ret i32 [[X]]
;
%assume = icmp sge i32 %x, 0
call void @llvm.assume(i1 %assume)