[llvm] 2622b2f - [ValueTracking] Use `select` condition to help determine if `select` is non-zero

Noah Goldstein via llvm-commits llvm-commits at lists.llvm.org
Tue May 23 11:57:08 PDT 2023 

Author: Noah Goldstein
Date: 2023-05-23T13:52:40-05:00
New Revision: 2622b2f409f7a7a51f11d5eab3976785b47c1a7b

URL: https://github.com/llvm/llvm-project/commit/2622b2f409f7a7a51f11d5eab3976785b47c1a7b
DIFF: https://github.com/llvm/llvm-project/commit/2622b2f409f7a7a51f11d5eab3976785b47c1a7b.diff

LOG: [ValueTracking] Use `select` condition to help determine if `select` is non-zero

In `select c, x, y` the condition `c` dominates the resulting `x` or
`y` chosen by the `select`. This adds logic to `isKnownNonZero` to try
and use the `icmp` for the `c` condition to see if it implies the
select `x` or `y` are known non-zero.

For example in:
    ```
    %c = icmp ugt i8 %x, %C
    %r = select i1 %c, i8 %x, i8 %y
    ```
    The true arm of select `%x` is non-zero (when "returned" by the
    `select`) because `%c` being true implies `%x` is non-zero.

Alive2 Links (with `x {pred} C`):
    - EQ  iff `C != 0`:
        - https://alive2.llvm.org/ce/z/umLabn
    - NE  iff `C == 0`:
        - https://alive2.llvm.org/ce/z/DQvy8Y
    - UGT [always]:
        - https://alive2.llvm.org/ce/z/HBkjgQ
    - UGE iff `C != 0`:
        - https://alive2.llvm.org/ce/z/LDNifB
    - SGT iff `C s>= 0`:
        - https://alive2.llvm.org/ce/z/QzWDj3
    - SGE iff `C s> 0`:
        - https://alive2.llvm.org/ce/z/rR4g3D
    - SLT iff `C s<= 0`:
        - https://alive2.llvm.org/ce/z/uysayx
    - SLE iff `C s< 0`:
        - https://alive2.llvm.org/ce/z/2jYc7e

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D147900

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Analysis/ValueTracking/select-known-non-zero-const.ll
    llvm/test/Analysis/ValueTracking/select-known-non-zero.ll
    llvm/test/Transforms/InstSimplify/compare.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 39c665f43f2f..ee6c39bc0036 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -580,6 +580,11 @@ bool llvm::isValidAssumeForContext(const Instruction *Inv,
   return false;
 }
 
+// TODO: cmpExcludesZero misses many cases where `RHS` is non-constant but
+// we still have enough information about `RHS` to conclude non-zero. For
+// example Pred=EQ, RHS=isKnownNonZero. cmpExcludesZero is called in loops
+// so the extra compile time may not be worth it, but possibly a second API
+// should be created for use outside of loops.
 static bool cmpExcludesZero(CmpInst::Predicate Pred, const Value *RHS) {
   // v u> y implies v != 0.
   if (Pred == ICmpInst::ICMP_UGT)
@@ -2882,12 +2887,38 @@ bool isKnownNonZero(const Value *V, const APInt &DemandedElts, unsigned Depth,
     return (XKnown.countMaxTrailingZeros() + YKnown.countMaxTrailingZeros()) <
            BitWidth;
   }
-  case Instruction::Select:
+  case Instruction::Select: {
     // (C ? X : Y) != 0 if X != 0 and Y != 0.
-    if (isKnownNonZero(I->getOperand(1), DemandedElts, Depth, Q) &&
-        isKnownNonZero(I->getOperand(2), DemandedElts, Depth, Q))
+
+    // First check if the arm is non-zero using `isKnownNonZero`. If that fails,
+    // then see if the select condition implies the arm is non-zero. For example
+    // (X != 0 ? X : Y), we know the true arm is non-zero as the `X` "return" is
+    // dominated by `X != 0`.
+    auto SelectArmIsNonZero = [&](bool IsTrueArm) {
+      Value *Op;
+      Op = IsTrueArm ? I->getOperand(1) : I->getOperand(2);
+      // Op is trivially non-zero.
+      if (isKnownNonZero(Op, DemandedElts, Depth, Q))
+        return true;
+
+      // The condition of the select dominates the true/false arm. Check if the
+      // condition implies that a given arm is non-zero.
+      Value *X;
+      CmpInst::Predicate Pred;
+      if (!match(I->getOperand(0), m_c_ICmp(Pred, m_Specific(Op), m_Value(X))))
+        return false;
+
+      if (!IsTrueArm)
+        Pred = ICmpInst::getInversePredicate(Pred);
+
+      return cmpExcludesZero(Pred, X);
+    };
+
+    if (SelectArmIsNonZero(/* IsTrueArm */ true) &&
+        SelectArmIsNonZero(/* IsTrueArm */ false))
       return true;
     break;
+  }
   case Instruction::PHI: {
     auto *PN = cast<PHINode>(I);
     if (Q.IIQ.UseInstrInfo && isNonZeroRecurrence(PN))

diff  --git a/llvm/test/Analysis/ValueTracking/select-known-non-zero-const.ll b/llvm/test/Analysis/ValueTracking/select-known-non-zero-const.ll
index 1365cd55c691..c73c369b5cdd 100644
--- a/llvm/test/Analysis/ValueTracking/select-known-non-zero-const.ll
+++ b/llvm/test/Analysis/ValueTracking/select-known-non-zero-const.ll
@@ -4,11 +4,7 @@
 declare void @llvm.assume(i1)
 define <2 x i1> @select_v_ne_z(<2 x i8> %v, <2 x i8> %yy) {
 ; CHECK-LABEL: @select_v_ne_z(
-; CHECK-NEXT:    [[Y:%.*]] = or <2 x i8> [[YY:%.*]], <i8 1, i8 1>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <2 x i8> [[V:%.*]], zeroinitializer
-; CHECK-NEXT:    [[S:%.*]] = select <2 x i1> [[CMP]], <2 x i8> [[V]], <2 x i8> [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq <2 x i8> [[S]], zeroinitializer
-; CHECK-NEXT:    ret <2 x i1> [[R]]
+; CHECK-NEXT:    ret <2 x i1> zeroinitializer
 ;
   %y = or <2 x i8> %yy, <i8 1, i8 1>
   %cmp = icmp ne <2 x i8> %v, zeroinitializer
@@ -38,10 +34,7 @@ define i1 @select_v_eq_nz(i8 %v, i8 %y) {
 ; CHECK-LABEL: @select_v_eq_nz(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 44, [[V:%.*]]
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[V]], i8 [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -55,10 +48,7 @@ define i1 @inv_select_v_ugt_nz(i8 %v, i8 %C, i8 %y) {
 ; CHECK-LABEL: @inv_select_v_ugt_nz(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i8 14, [[V:%.*]]
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[V]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -72,10 +62,7 @@ define i1 @inv_select_v_ugt_fail(i8 %v, i8 %C, i8 %y) {
 ; CHECK-LABEL: @inv_select_v_ugt_fail(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i8 -2, [[V:%.*]]
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[V]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -87,11 +74,7 @@ define i1 @inv_select_v_ugt_fail(i8 %v, i8 %C, i8 %y) {
 
 define <2 x i1> @select_v_ult(<2 x i8> %v, <2 x i8> %C, <2 x i8> %yy) {
 ; CHECK-LABEL: @select_v_ult(
-; CHECK-NEXT:    [[Y:%.*]] = or <2 x i8> [[YY:%.*]], <i8 1, i8 1>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ult <2 x i8> [[C:%.*]], [[V:%.*]]
-; CHECK-NEXT:    [[S:%.*]] = select <2 x i1> [[CMP]], <2 x i8> [[V]], <2 x i8> [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq <2 x i8> [[S]], zeroinitializer
-; CHECK-NEXT:    ret <2 x i1> [[R]]
+; CHECK-NEXT:    ret <2 x i1> zeroinitializer
 ;
   %y = or <2 x i8> %yy, <i8 1, i8 1>
   %cmp = icmp ult <2 x i8> %C, %v
@@ -102,11 +85,7 @@ define <2 x i1> @select_v_ult(<2 x i8> %v, <2 x i8> %C, <2 x i8> %yy) {
 
 define <2 x i1> @select_v_uge_nz(<2 x i8> %v, <2 x i8> %yy) {
 ; CHECK-LABEL: @select_v_uge_nz(
-; CHECK-NEXT:    [[Y:%.*]] = or <2 x i8> [[YY:%.*]], <i8 1, i8 1>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp uge <2 x i8> [[V:%.*]], <i8 1, i8 1>
-; CHECK-NEXT:    [[S:%.*]] = select <2 x i1> [[CMP]], <2 x i8> [[V]], <2 x i8> [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq <2 x i8> [[S]], zeroinitializer
-; CHECK-NEXT:    ret <2 x i1> [[R]]
+; CHECK-NEXT:    ret <2 x i1> zeroinitializer
 ;
   %y = or <2 x i8> %yy, <i8 1, i8 1>
   %cmp = icmp uge <2 x i8> %v, <i8 1, i8 1>
@@ -119,10 +98,7 @@ define i1 @inv_select_v_ule(i8 %v, i8 %y) {
 ; CHECK-LABEL: @inv_select_v_ule(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ule i8 [[V:%.*]], 4
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[V]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -136,10 +112,7 @@ define i1 @select_v_sgt_nonneg(i8 %v, i8 %y) {
 ; CHECK-LABEL: @select_v_sgt_nonneg(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 [[V:%.*]], 0
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[V]], i8 [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -170,10 +143,7 @@ define i1 @inv_select_v_sgt_neg(i8 %v, i8 %y) {
 ; CHECK-LABEL: @inv_select_v_sgt_neg(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 [[V:%.*]], -1
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[V]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -187,10 +157,7 @@ define i1 @inv_select_v_sgt_nonneg_nz(i8 %v, i8 %C, i8 %y) {
 ; CHECK-LABEL: @inv_select_v_sgt_nonneg_nz(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 99, [[V:%.*]]
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[V]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -204,10 +171,7 @@ define i1 @select_v_slt_nonneg(i8 %v, i8 %y) {
 ; CHECK-LABEL: @select_v_slt_nonneg(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i8 0, [[V:%.*]]
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[V]], i8 [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -238,10 +202,7 @@ define i1 @select_v_slt_neg(i8 %v, i8 %y) {
 ; CHECK-LABEL: @select_v_slt_neg(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i8 [[V:%.*]], -1
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[V]], i8 [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -255,10 +216,7 @@ define i1 @select_v_sge_nonneg_nz(i8 %v, i8 %y) {
 ; CHECK-LABEL: @select_v_sge_nonneg_nz(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i8 [[V:%.*]], 1
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[V]], i8 [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -272,10 +230,7 @@ define i1 @select_v_sge_neg(i8 %v, i8 %y) {
 ; CHECK-LABEL: @select_v_sge_neg(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i8 -3, [[V:%.*]]
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[V]], i8 [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -289,10 +244,7 @@ define i1 @inv_select_v_sge_z(i8 %v, i8 %y) {
 ; CHECK-LABEL: @inv_select_v_sge_z(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i8 [[V:%.*]], 0
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[V]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -306,10 +258,7 @@ define i1 @inv_select_v_sge_fail(i8 %v, i8 %C, i8 %y) {
 ; CHECK-LABEL: @inv_select_v_sge_fail(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i8 [[V:%.*]], -44
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[V]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -323,10 +272,7 @@ define i1 @select_v_sle_neg(i8 %v, i8 %y) {
 ; CHECK-LABEL: @select_v_sle_neg(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i8 [[V:%.*]], -1
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[V]], i8 [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -340,10 +286,7 @@ define i1 @select_v_sle_nonneg_nz(i8 %v, i8 %y) {
 ; CHECK-LABEL: @select_v_sle_nonneg_nz(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i8 1, [[V:%.*]]
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[V]], i8 [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)
@@ -374,10 +317,7 @@ define i1 @inv_select_v_sle_nonneg(i8 %v, i8 %y) {
 ; CHECK-LABEL: @inv_select_v_sle_nonneg(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i8 [[V:%.*]], 0
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[V]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[S]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %ynz = icmp ne i8 %y, 0
   call void @llvm.assume(i1 %ynz)

diff  --git a/llvm/test/Analysis/ValueTracking/select-known-non-zero.ll b/llvm/test/Analysis/ValueTracking/select-known-non-zero.ll
index bcd830ed2f3d..8b1d2fd0181d 100644
--- a/llvm/test/Analysis/ValueTracking/select-known-non-zero.ll
+++ b/llvm/test/Analysis/ValueTracking/select-known-non-zero.ll
@@ -2,6 +2,7 @@
 ; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
 
 declare void @llvm.assume(i1)
+
 define i1 @select_v_ne_fail(i8 %v, i8 %C, i8 %y) {
 ; CHECK-LABEL: @select_v_ne_fail(
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0

diff  --git a/llvm/test/Transforms/InstSimplify/compare.ll b/llvm/test/Transforms/InstSimplify/compare.ll
index 260d34519e11..c62399c119c9 100644
--- a/llvm/test/Transforms/InstSimplify/compare.ll
+++ b/llvm/test/Transforms/InstSimplify/compare.ll
@@ -729,10 +729,7 @@ define i1 @select5(i32 %x) {
 
 define i1 @select6(i32 %x) {
 ; CHECK-LABEL: @select6(
-; CHECK-NEXT:    [[C:%.*]] = icmp sgt i32 [[X:%.*]], 0
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[C]], i32 [[X]], i32 4
-; CHECK-NEXT:    [[C2:%.*]] = icmp eq i32 [[S]], 0
-; CHECK-NEXT:    ret i1 [[C2]]
+; CHECK-NEXT:    ret i1 false
 ;
   %c = icmp sgt i32 %x, 0
   %s = select i1 %c, i32 %x, i32 4

More information about the llvm-commits mailing list