[llvm] r349369 - [InstSimplify] Simplify saturating add/sub + icmp
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 17 09:45:19 PST 2018
Author: nikic
Date: Mon Dec 17 09:45:18 2018
New Revision: 349369
URL: http://llvm.org/viewvc/llvm-project?rev=349369&view=rev
Log:
[InstSimplify] Simplify saturating add/sub + icmp
If a saturating add/sub has one constant operand, then we can
determine the possible range of outputs it can produce, and simplify
an icmp comparison based on that.
The implementation is based on a similar existing mechanism for
simplifying binary operator + icmps.
Differential Revision: https://reviews.llvm.org/D55735
Modified:
llvm/trunk/lib/Analysis/InstructionSimplify.cpp
llvm/trunk/test/Transforms/InstSimplify/saturating-add-sub.ll
Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=349369&r1=349368&r2=349369&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Mon Dec 17 09:45:18 2018
@@ -2630,6 +2630,70 @@ static void setLimitsForBinOp(BinaryOper
}
}
+/// Some intrinsics with a constant operand have an easy-to-compute range of
+/// outputs. This can be used to fold a comparison to always true or always
+/// false.
+static void setLimitsForIntrinsic(IntrinsicInst &II, APInt &Lower,
+ APInt &Upper) {
+ unsigned Width = Lower.getBitWidth();
+ const APInt *C;
+ switch (II.getIntrinsicID()) {
+ case Intrinsic::uadd_sat:
+ // uadd.sat(x, C) produces [C, UINT_MAX].
+ if (match(II.getOperand(0), m_APInt(C)) ||
+ match(II.getOperand(1), m_APInt(C)))
+ Lower = *C;
+ break;
+ case Intrinsic::sadd_sat:
+ if (match(II.getOperand(0), m_APInt(C)) ||
+ match(II.getOperand(1), m_APInt(C))) {
+ if (C->isNegative()) {
+ // sadd.sat(x, -C) produces [SINT_MIN, SINT_MAX + (-C)].
+ Lower = APInt::getSignedMinValue(Width);
+ Upper = APInt::getSignedMaxValue(Width) + *C + 1;
+ } else {
+ // sadd.sat(x, +C) produces [SINT_MIN + C, SINT_MAX].
+ Lower = APInt::getSignedMinValue(Width) + *C;
+ Upper = APInt::getSignedMaxValue(Width) + 1;
+ }
+ }
+ break;
+ case Intrinsic::usub_sat:
+ // usub.sat(C, x) produces [0, C].
+ if (match(II.getOperand(0), m_APInt(C)))
+ Upper = *C + 1;
+ // usub.sat(x, C) produces [0, UINT_MAX - C].
+ else if (match(II.getOperand(1), m_APInt(C)))
+ Upper = APInt::getMaxValue(Width) - *C + 1;
+ break;
+ case Intrinsic::ssub_sat:
+ if (match(II.getOperand(0), m_APInt(C))) {
+ if (C->isNegative()) {
+ // ssub.sat(-C, x) produces [SINT_MIN, -SINT_MIN + (-C)].
+ Lower = APInt::getSignedMinValue(Width);
+ Upper = *C - APInt::getSignedMinValue(Width) + 1;
+ } else {
+ // ssub.sat(+C, x) produces [-SINT_MAX + C, SINT_MAX].
+ Lower = *C - APInt::getSignedMaxValue(Width);
+ Upper = APInt::getSignedMaxValue(Width) + 1;
+ }
+ } else if (match(II.getOperand(1), m_APInt(C))) {
+ if (C->isNegative()) {
+ // ssub.sat(x, -C) produces [SINT_MIN - (-C), SINT_MAX]:
+ Lower = APInt::getSignedMinValue(Width) - *C;
+ Upper = APInt::getSignedMaxValue(Width) + 1;
+ } else {
+ // ssub.sat(x, +C) produces [SINT_MIN, SINT_MAX - C].
+ Lower = APInt::getSignedMinValue(Width);
+ Upper = APInt::getSignedMaxValue(Width) - *C + 1;
+ }
+ }
+ break;
+ default:
+ break;
+ }
+}
+
static Value *simplifyICmpWithConstant(CmpInst::Predicate Pred, Value *LHS,
Value *RHS, const InstrInfoQuery &IIQ) {
Type *ITy = GetCompareTy(RHS); // The return type.
@@ -2663,6 +2727,8 @@ static Value *simplifyICmpWithConstant(C
APInt Upper = APInt(Width, 0);
if (auto *BO = dyn_cast<BinaryOperator>(LHS))
setLimitsForBinOp(*BO, Lower, Upper, IIQ);
+ else if (auto *II = dyn_cast<IntrinsicInst>(LHS))
+ setLimitsForIntrinsic(*II, Lower, Upper);
ConstantRange LHS_CR =
Lower != Upper ? ConstantRange(Lower, Upper) : ConstantRange(Width, true);
Modified: llvm/trunk/test/Transforms/InstSimplify/saturating-add-sub.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/saturating-add-sub.ll?rev=349369&r1=349368&r2=349369&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/saturating-add-sub.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/saturating-add-sub.ll Mon Dec 17 09:45:18 2018
@@ -408,9 +408,7 @@ define <2 x i8> @ssub_vector_same(<2 x i
define i1 @uadd_icmp_op0_known(i8 %a) {
; CHECK-LABEL: @uadd_icmp_op0_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.uadd.sat.i8(i8 10, i8 [[A:%.*]])
-; CHECK-NEXT: [[C:%.*]] = icmp uge i8 [[B]], 10
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.uadd.sat.i8(i8 10, i8 %a)
%c = icmp uge i8 %b, 10
@@ -430,9 +428,7 @@ define i1 @uadd_icmp_op0_unknown(i8 %a)
define i1 @uadd_icmp_op1_known(i8 %a) {
; CHECK-LABEL: @uadd_icmp_op1_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.uadd.sat.i8(i8 [[A:%.*]], i8 10)
-; CHECK-NEXT: [[C:%.*]] = icmp uge i8 [[B]], 10
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.uadd.sat.i8(i8 %a, i8 10)
%c = icmp uge i8 %b, 10
@@ -452,9 +448,7 @@ define i1 @uadd_icmp_op1_unknown(i8 %a)
define i1 @sadd_icmp_op0_pos_known(i8 %a) {
; CHECK-LABEL: @sadd_icmp_op0_pos_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.sadd.sat.i8(i8 10, i8 [[A:%.*]])
-; CHECK-NEXT: [[C:%.*]] = icmp sge i8 [[B]], -118
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.sadd.sat.i8(i8 10, i8 %a)
%c = icmp sge i8 %b, -118
@@ -474,9 +468,7 @@ define i1 @sadd_icmp_op0_pos_unknown(i8
define i1 @sadd_icmp_op0_neg_known(i8 %a) {
; CHECK-LABEL: @sadd_icmp_op0_neg_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.sadd.sat.i8(i8 -10, i8 [[A:%.*]])
-; CHECK-NEXT: [[C:%.*]] = icmp sle i8 [[B]], 117
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.sadd.sat.i8(i8 -10, i8 %a)
%c = icmp sle i8 %b, 117
@@ -496,9 +488,7 @@ define i1 @sadd_icmp_op0_neg_unknown(i8
define i1 @sadd_icmp_op1_pos_known(i8 %a) {
; CHECK-LABEL: @sadd_icmp_op1_pos_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.sadd.sat.i8(i8 [[A:%.*]], i8 10)
-; CHECK-NEXT: [[C:%.*]] = icmp sge i8 [[B]], -118
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.sadd.sat.i8(i8 %a, i8 10)
%c = icmp sge i8 %b, -118
@@ -518,9 +508,7 @@ define i1 @sadd_icmp_op1_pos_unknown(i8
define i1 @sadd_icmp_op1_neg_known(i8 %a) {
; CHECK-LABEL: @sadd_icmp_op1_neg_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.sadd.sat.i8(i8 [[A:%.*]], i8 -10)
-; CHECK-NEXT: [[C:%.*]] = icmp sle i8 [[B]], 117
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.sadd.sat.i8(i8 %a, i8 -10)
%c = icmp sle i8 %b, 117
@@ -540,9 +528,7 @@ define i1 @sadd_icmp_op1_neg_unknown(i8
define i1 @usub_icmp_op0_known(i8 %a) {
; CHECK-LABEL: @usub_icmp_op0_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.usub.sat.i8(i8 10, i8 [[A:%.*]])
-; CHECK-NEXT: [[C:%.*]] = icmp ule i8 [[B]], 10
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.usub.sat.i8(i8 10, i8 %a)
%c = icmp ule i8 %b, 10
@@ -562,9 +548,7 @@ define i1 @usub_icmp_op0_unknown(i8 %a)
define i1 @usub_icmp_op1_known(i8 %a) {
; CHECK-LABEL: @usub_icmp_op1_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[A:%.*]], i8 10)
-; CHECK-NEXT: [[C:%.*]] = icmp ule i8 [[B]], -11
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.usub.sat.i8(i8 %a, i8 10)
%c = icmp ule i8 %b, 245
@@ -584,9 +568,7 @@ define i1 @usub_icmp_op1_unknown(i8 %a)
define i1 @ssub_icmp_op0_pos_known(i8 %a) {
; CHECK-LABEL: @ssub_icmp_op0_pos_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.ssub.sat.i8(i8 10, i8 [[A:%.*]])
-; CHECK-NEXT: [[C:%.*]] = icmp sge i8 [[B]], -117
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.ssub.sat.i8(i8 10, i8 %a)
%c = icmp sge i8 %b, -117
@@ -606,9 +588,7 @@ define i1 @ssub_icmp_op0_pos_unknown(i8
define i1 @ssub_icmp_op0_neg_known(i8 %a) {
; CHECK-LABEL: @ssub_icmp_op0_neg_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.ssub.sat.i8(i8 -10, i8 [[A:%.*]])
-; CHECK-NEXT: [[C:%.*]] = icmp sle i8 [[B]], 118
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.ssub.sat.i8(i8 -10, i8 %a)
%c = icmp sle i8 %b, 118
@@ -629,9 +609,7 @@ define i1 @ssub_icmp_op0_neg_unknown(i8
; Peculiar case: ssub.sat(0, x) is never signed min.
define i1 @ssub_icmp_op0_zero(i8 %a) {
; CHECK-LABEL: @ssub_icmp_op0_zero(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.ssub.sat.i8(i8 0, i8 [[A:%.*]])
-; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[B]], -128
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.ssub.sat.i8(i8 0, i8 %a)
%c = icmp ne i8 %b, -128
@@ -640,9 +618,7 @@ define i1 @ssub_icmp_op0_zero(i8 %a) {
define i1 @ssub_icmp_op1_pos_known(i8 %a) {
; CHECK-LABEL: @ssub_icmp_op1_pos_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.ssub.sat.i8(i8 [[A:%.*]], i8 10)
-; CHECK-NEXT: [[C:%.*]] = icmp sle i8 [[B]], 117
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.ssub.sat.i8(i8 %a, i8 10)
%c = icmp sle i8 %b, 117
@@ -662,9 +638,7 @@ define i1 @ssub_icmp_op1_pos_unknown(i8
define i1 @ssub_icmp_op1_neg_known(i8 %a) {
; CHECK-LABEL: @ssub_icmp_op1_neg_known(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.ssub.sat.i8(i8 [[A:%.*]], i8 -10)
-; CHECK-NEXT: [[C:%.*]] = icmp sge i8 [[B]], -118
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.ssub.sat.i8(i8 %a, i8 -10)
%c = icmp sge i8 %b, -118
@@ -684,9 +658,7 @@ define i1 @ssub_icmp_op1_neg_unknown(i8
define i1 @ssub_icmp_op1_smin(i8 %a) {
; CHECK-LABEL: @ssub_icmp_op1_smin(
-; CHECK-NEXT: [[B:%.*]] = call i8 @llvm.ssub.sat.i8(i8 [[A:%.*]], i8 -128)
-; CHECK-NEXT: [[C:%.*]] = icmp sge i8 [[B]], 0
-; CHECK-NEXT: ret i1 [[C]]
+; CHECK-NEXT: ret i1 true
;
%b = call i8 @llvm.ssub.sat.i8(i8 %a, i8 -128)
%c = icmp sge i8 %b, 0
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