[llvm] r362911 - [InstCombine] foldICmpWithLowBitMaskedVal(): 'icmp sgt/sle': avoid miscompiles
Roman Lebedev via llvm-commits
llvm-commits at lists.llvm.org
Sun Jun 9 09:30:42 PDT 2019
Author: lebedevri
Date: Sun Jun 9 09:30:42 2019
New Revision: 362911
URL: http://llvm.org/viewvc/llvm-project?rev=362911&view=rev
Log:
[InstCombine] foldICmpWithLowBitMaskedVal(): 'icmp sgt/sle': avoid miscompiles
A precondition 'x != 0' was forgotten by me:
https://rise4fun.com/Alive/JFNP
https://rise4fun.com/Alive/jHvL
These 4 folds with non-constants could be re-enabled,
but for now let's go for the simplest solution.
https://bugs.llvm.org/show_bug.cgi?id=42198
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll
llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=362911&r1=362910&r2=362911&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Sun Jun 9 09:30:42 2019
@@ -3110,6 +3110,10 @@ static Value *foldICmpWithLowBitMaskedVa
// x s> x & (-1 >> y) -> x s> (-1 >> y)
if (X != I.getOperand(0)) // X must be on LHS of comparison!
return nullptr; // Ignore the other case.
+ if (!match(M, m_Constant())) // Can not do this fold with non-constant.
+ return nullptr;
+ if (!match(M, m_NonNegative())) // Must not have any -1 vector elements.
+ return nullptr;
DstPred = ICmpInst::Predicate::ICMP_SGT;
break;
case ICmpInst::Predicate::ICMP_SGE:
@@ -3136,6 +3140,10 @@ static Value *foldICmpWithLowBitMaskedVa
// x s<= x & (-1 >> y) -> x s<= (-1 >> y)
if (X != I.getOperand(0)) // X must be on LHS of comparison!
return nullptr; // Ignore the other case.
+ if (!match(M, m_Constant())) // Can not do this fold with non-constant.
+ return nullptr;
+ if (!match(M, m_NonNegative())) // Must not have any -1 vector elements.
+ return nullptr;
DstPred = ICmpInst::Predicate::ICMP_SLE;
break;
default:
Modified: llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll?rev=362911&r1=362910&r2=362911&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll Sun Jun 9 09:30:42 2019
@@ -174,8 +174,9 @@ define i1 @pv(i8 %y) {
; CHECK-LABEL: @pv(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
-; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i8 [[X]], [[TMP0]]
-; CHECK-NEXT: ret i1 [[TMP1]]
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[TMP0]], [[X]]
+; CHECK-NEXT: [[RET:%.*]] = icmp sgt i8 [[X]], [[TMP1]]
+; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
@@ -187,8 +188,9 @@ define i1 @pv(i8 %y) {
define <2 x i1> @n3_vec() {
; CHECK-LABEL: @n3_vec(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
-; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <2 x i8> [[X]], <i8 3, i8 -1>
-; CHECK-NEXT: ret <2 x i1> [[TMP1]]
+; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X]], <i8 3, i8 -1>
+; CHECK-NEXT: [[RET:%.*]] = icmp sgt <2 x i8> [[X]], [[TMP0]]
+; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 -1>
@@ -199,8 +201,9 @@ define <2 x i1> @n3_vec() {
define <3 x i1> @n4_vec() {
; CHECK-LABEL: @n4_vec(
; CHECK-NEXT: [[X:%.*]] = call <3 x i8> @gen3x8()
-; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <3 x i8> [[X]], <i8 3, i8 undef, i8 -1>
-; CHECK-NEXT: ret <3 x i1> [[TMP1]]
+; CHECK-NEXT: [[TMP0:%.*]] = and <3 x i8> [[X]], <i8 3, i8 undef, i8 -1>
+; CHECK-NEXT: [[RET:%.*]] = icmp sgt <3 x i8> [[X]], [[TMP0]]
+; CHECK-NEXT: ret <3 x i1> [[RET]]
;
%x = call <3 x i8> @gen3x8()
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 -1>
@@ -215,8 +218,9 @@ define i1 @cv0_GOOD(i8 %y) {
; CHECK-LABEL: @cv0_GOOD(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
-; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt i8 [[X]], [[TMP0]]
-; CHECK-NEXT: ret i1 [[TMP1]]
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[TMP0]], [[X]]
+; CHECK-NEXT: [[RET:%.*]] = icmp sgt i8 [[X]], [[TMP1]]
+; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
Modified: llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll?rev=362911&r1=362910&r2=362911&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll Sun Jun 9 09:30:42 2019
@@ -174,8 +174,9 @@ define i1 @pv(i8 %y) {
; CHECK-LABEL: @pv(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
-; CHECK-NEXT: [[TMP1:%.*]] = icmp sle i8 [[X]], [[TMP0]]
-; CHECK-NEXT: ret i1 [[TMP1]]
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[TMP0]], [[X]]
+; CHECK-NEXT: [[RET:%.*]] = icmp sle i8 [[X]], [[TMP1]]
+; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
@@ -187,8 +188,9 @@ define i1 @pv(i8 %y) {
define <2 x i1> @n3_vec() {
; CHECK-LABEL: @n3_vec(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
-; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <2 x i8> [[X]], <i8 4, i8 0>
-; CHECK-NEXT: ret <2 x i1> [[TMP1]]
+; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X]], <i8 3, i8 -1>
+; CHECK-NEXT: [[RET:%.*]] = icmp sle <2 x i8> [[X]], [[TMP0]]
+; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 -1>
@@ -199,8 +201,9 @@ define <2 x i1> @n3_vec() {
define <3 x i1> @n4_vec() {
; CHECK-LABEL: @n4_vec(
; CHECK-NEXT: [[X:%.*]] = call <3 x i8> @gen3x8()
-; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <3 x i8> [[X]], <i8 4, i8 undef, i8 0>
-; CHECK-NEXT: ret <3 x i1> [[TMP1]]
+; CHECK-NEXT: [[TMP0:%.*]] = and <3 x i8> [[X]], <i8 3, i8 undef, i8 -1>
+; CHECK-NEXT: [[RET:%.*]] = icmp sle <3 x i8> [[X]], [[TMP0]]
+; CHECK-NEXT: ret <3 x i1> [[RET]]
;
%x = call <3 x i8> @gen3x8()
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 -1>
@@ -214,8 +217,9 @@ define i1 @cv0_GOOD(i8 %y) {
; CHECK-LABEL: @cv0_GOOD(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
-; CHECK-NEXT: [[TMP1:%.*]] = icmp sle i8 [[X]], [[TMP0]]
-; CHECK-NEXT: ret i1 [[TMP1]]
+; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[TMP0]], [[X]]
+; CHECK-NEXT: [[RET:%.*]] = icmp sle i8 [[X]], [[TMP1]]
+; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
More information about the llvm-commits
mailing list