Added inst combine tarnsform for (1 << X) & C pattrens where C is (some PowerOf2 - 1)
This patch can handles following cases from http://nondot.org/sabre/LLVMNotes/InstCombine.txt
"((1 << X) & 7) == 0" ==> "X > 2"
"((1 << X) & 7) != 0" ==> "X < 3".
Differential Revision: http://reviews.llvm.org/D3678
llvm-svn: 210007
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 79cd1fb..3d90a37 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2540,7 +2540,7 @@
// bit is set. If the comparison is against zero, then this is a check
// to see if *that* bit is set.
APInt Op0KnownZeroInverted = ~Op0KnownZero;
- if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
+ if (~Op1KnownZero == 0) {
// If the LHS is an AND with the same constant, look through it.
Value *LHS = nullptr;
ConstantInt *LHSC = nullptr;
@@ -2550,11 +2550,19 @@
// If the LHS is 1 << x, and we know the result is a power of 2 like 8,
// then turn "((1 << x)&8) == 0" into "x != 3".
+ // or turn "((1 << x)&7) == 0" into "x > 2".
Value *X = nullptr;
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
- unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
- return new ICmpInst(ICmpInst::ICMP_NE, X,
- ConstantInt::get(X->getType(), CmpVal));
+ APInt ValToCheck = Op0KnownZeroInverted;
+ if (ValToCheck.isPowerOf2()) {
+ unsigned CmpVal = ValToCheck.countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_NE, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ } else if ((++ValToCheck).isPowerOf2()) {
+ unsigned CmpVal = ValToCheck.countTrailingZeros() - 1;
+ return new ICmpInst(ICmpInst::ICMP_UGT, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ }
}
// If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
@@ -2577,7 +2585,7 @@
// bit is set. If the comparison is against zero, then this is a check
// to see if *that* bit is set.
APInt Op0KnownZeroInverted = ~Op0KnownZero;
- if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
+ if (~Op1KnownZero == 0) {
// If the LHS is an AND with the same constant, look through it.
Value *LHS = nullptr;
ConstantInt *LHSC = nullptr;
@@ -2587,11 +2595,19 @@
// If the LHS is 1 << x, and we know the result is a power of 2 like 8,
// then turn "((1 << x)&8) != 0" into "x == 3".
+ // or turn "((1 << x)&7) != 0" into "x < 3".
Value *X = nullptr;
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
- unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
- return new ICmpInst(ICmpInst::ICMP_EQ, X,
- ConstantInt::get(X->getType(), CmpVal));
+ APInt ValToCheck = Op0KnownZeroInverted;
+ if (ValToCheck.isPowerOf2()) {
+ unsigned CmpVal = ValToCheck.countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_EQ, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ } else if ((++ValToCheck).isPowerOf2()) {
+ unsigned CmpVal = ValToCheck.countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_ULT, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ }
}
// If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index fd7514d..dcfff99 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -166,6 +166,14 @@
; CHECK-NEXT: %cmp = icmp ne i32 %x, 3
}
+define i1 @test17a(i32 %x) nounwind {
+ %shl = shl i32 1, %x
+ %and = and i32 %shl, 7
+ %cmp = icmp eq i32 %and, 0
+ ret i1 %cmp
+; CHECK-LABEL: @test17a(
+; CHECK-NEXT: %cmp = icmp ugt i32 %x, 2
+}
define i1 @test18(i32 %x) nounwind {
%sh = lshr i32 8, %x
@@ -194,6 +202,15 @@
; CHECK-NEXT: %cmp = icmp eq i32 %x, 3
}
+define i1 @test20a(i32 %x) nounwind {
+ %shl = shl i32 1, %x
+ %and = and i32 %shl, 7
+ %cmp = icmp ne i32 %and, 0
+ ret i1 %cmp
+; CHECK-LABEL: @test20a(
+; CHECK-NEXT: %cmp = icmp ult i32 %x, 3
+}
+
define i1 @test21(i8 %x, i8 %y) {
; CHECK-LABEL: @test21(
; CHECK-NOT: or i8