[llvm] fbb40df - [ValueTracking] In `isKnownToBeAPowerOfTwo` an `i1` value is always true if `OrZero` is set

[Noah Goldstein via llvm-commits]

Author: Noah Goldstein
Date: 2023-08-09T14:42:55-05:00
New Revision: fbb40df2bff00f6653b087fa2fe25e0d60de2389

URL: https://github.com/llvm/llvm-project/commit/fbb40df2bff00f6653b087fa2fe25e0d60de2389
DIFF: https://github.com/llvm/llvm-project/commit/fbb40df2bff00f6653b087fa2fe25e0d60de2389.diff

LOG: [ValueTracking] In `isKnownToBeAPowerOfTwo` an `i1` value is always true if `OrZero` is set

This is trivially true.

Differential Revision: https://reviews.llvm.org/D157310

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Analysis/ValueTracking/known-power-of-two.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d82c83c9a33269..936bddfcdbdd11 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2009,6 +2009,10 @@ bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
   if (isa<Constant>(V))
     return OrZero ? match(V, m_Power2OrZero()) : match(V, m_Power2());
 
+  // i1 is by definition a power of 2 or zero.
+  if (OrZero && V->getType()->getScalarSizeInBits() == 1)
+    return true;
+
   auto *I = dyn_cast<Instruction>(V);
   if (!I)
     return false;

diff  --git a/llvm/test/Analysis/ValueTracking/known-power-of-two.ll b/llvm/test/Analysis/ValueTracking/known-power-of-two.ll
index 002147b390ce2c..b86cf59fa2046c 100644
--- a/llvm/test/Analysis/ValueTracking/known-power-of-two.ll
+++ b/llvm/test/Analysis/ValueTracking/known-power-of-two.ll
@@ -619,8 +619,7 @@ define i16 @i1_is_pow2_or_zero(i1 %x, i16 %y) {
 ; CHECK-LABEL: define i16 @i1_is_pow2_or_zero
 ; CHECK-SAME: (i1 [[X:%.*]], i16 [[Y:%.*]]) {
 ; CHECK-NEXT:    [[XX:%.*]] = zext i1 [[X]] to i16
-; CHECK-NEXT:    [[YY:%.*]] = xor i16 [[XX]], [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = call i16 @llvm.umax.i16(i16 [[YY]], i16 [[Y]])
+; CHECK-NEXT:    [[R:%.*]] = or i16 [[XX]], [[Y]]
 ; CHECK-NEXT:    ret i16 [[R]]
 ;
   %xx = zext i1 %x to i16
@@ -634,8 +633,7 @@ define i16 @i1_is_pow2_or_zero2(i1 %x, i16 %y0, i16 %z) {
 ; CHECK-SAME: (i1 [[X:%.*]], i16 [[Y0:%.*]], i16 [[Z:%.*]]) {
 ; CHECK-NEXT:    [[XX:%.*]] = zext i1 [[X]] to i16
 ; CHECK-NEXT:    [[Y:%.*]] = or i16 [[Y0]], [[Z]]
-; CHECK-NEXT:    [[YY:%.*]] = xor i16 [[Y]], [[XX]]
-; CHECK-NEXT:    [[R:%.*]] = call i16 @llvm.umax.i16(i16 [[YY]], i16 [[Y]])
+; CHECK-NEXT:    [[R:%.*]] = or i16 [[Y]], [[XX]]
 ; CHECK-NEXT:    ret i16 [[R]]
 ;
   %xx = zext i1 %x to i16