[PATCH] D153148: [InstCombine] Fold `(-1 + A) & B` into `A ? 0 : B` where A is effectively a bool

[Yingwei Zheng via Phabricator via llvm-commits]

dtcxzyw updated this revision to Diff 532391.
dtcxzyw retitled this revision from "[InstCombine] Fold `(-1 + zext(B)) & X` into `B ? 0 : X` where B is effectively a bool" to "[InstCombine] Fold `(-1 + A) & B` into `A ? 0 : B` where A is effectively a bool".
dtcxzyw edited the summary of this revision.
dtcxzyw added a comment.

fix comment and rebase


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153148/new/

https://reviews.llvm.org/D153148

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/test/Transforms/InstCombine/binop-cast.ll


Index: llvm/test/Transforms/InstCombine/binop-cast.ll
===================================================================
--- llvm/test/Transforms/InstCombine/binop-cast.ll
+++ llvm/test/Transforms/InstCombine/binop-cast.ll
@@ -257,3 +257,17 @@
   %r = xor i32 %sext, 42
   ret i32 %r
 }
+
+define i64 @PR63321(ptr %ptr, i64 %c) {
+; CHECK-LABEL: @PR63321(
+; CHECK-NEXT:    [[VAL:%.*]] = load i8, ptr [[PTR:%.*]], align 1, !range [[RNG0:![0-9]+]]
+; CHECK-NEXT:    [[DOTNOT:%.*]] = icmp eq i8 [[VAL]], 0
+; CHECK-NEXT:    [[RES:%.*]] = select i1 [[DOTNOT]], i64 [[C:%.*]], i64 0
+; CHECK-NEXT:    ret i64 [[RES]]
+;
+  %val = load i8, ptr %ptr, align 1, !range !{i8 0, i8 2}
+  %rhs = zext i8 %val to i64
+  %mask = add i64 -1, %rhs
+  %res = and i64 %mask, %c
+  ret i64 %res
+}
Index: llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2546,23 +2546,28 @@
   //       with binop identity constant. But creating a select with non-constant
   //       arm may not be reversible due to poison semantics. Is that a good
   //       canonicalization?
-  Value *A;
-  if (match(Op0, m_OneUse(m_SExt(m_Value(A)))) &&
-      A->getType()->isIntOrIntVectorTy(1))
-    return SelectInst::Create(A, Op1, Constant::getNullValue(Ty));
-  if (match(Op1, m_OneUse(m_SExt(m_Value(A)))) &&
+  Value *A, *B;
+  if (match(&I, m_c_And(m_OneUse(m_SExt(m_Value(A))), m_Value(B))) &&
       A->getType()->isIntOrIntVectorTy(1))
-    return SelectInst::Create(A, Op0, Constant::getNullValue(Ty));
+    return SelectInst::Create(A, B, Constant::getNullValue(Ty));
 
   // Similarly, a 'not' of the bool translates to a swap of the select arms:
-  // ~sext(A) & Op1 --> A ? 0 : Op1
-  // Op0 & ~sext(A) --> A ? 0 : Op0
-  if (match(Op0, m_Not(m_SExt(m_Value(A)))) &&
-      A->getType()->isIntOrIntVectorTy(1))
-    return SelectInst::Create(A, Constant::getNullValue(Ty), Op1);
-  if (match(Op1, m_Not(m_SExt(m_Value(A)))) &&
+  // ~sext(A) & B / B & ~sext(A) --> A ? 0 : B
+  if (match(&I, m_c_And(m_Not(m_SExt(m_Value(A))), m_Value(B))) &&
       A->getType()->isIntOrIntVectorTy(1))
-    return SelectInst::Create(A, Constant::getNullValue(Ty), Op0);
+    return SelectInst::Create(A, Constant::getNullValue(Ty), B);
+
+  // (-1 + A) & B --> A ? 0 : B where A is effectively a bool (zext of i1/<N x
+  // i1>, or inst with !range {0, 2}).
+  if (match(&I, m_c_And(m_c_Add(m_ZExtOrSelf(m_Value(A)), m_AllOnes()),
+                        m_Value(B))) &&
+      (A->getType()->isIntOrIntVectorTy(1) ||
+       KnownBits::ule(computeKnownBits(A, /* Depth */ 0, &I),
+                      KnownBits::makeConstant(APInt(
+                          A->getType()->getScalarSizeInBits(), 1))) == true))
+    return SelectInst::Create(
+        Builder.CreateTrunc(A, A->getType()->getWithNewBitWidth(1)),
+        Constant::getNullValue(Ty), B);
 
   // (iN X s>> (N-1)) & Y --> (X s< 0) ? Y : 0 -- with optional sext
   if (match(&I, m_c_And(m_OneUse(m_SExtOrSelf(


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