[llvm] r220162 - InstCombine: Optimize icmp eq/ne (shl Const2, A), Const1
David Majnemer
david.majnemer at gmail.com
Sun Oct 19 01:23:08 PDT 2014
Author: majnemer
Date: Sun Oct 19 03:23:08 2014
New Revision: 220162
URL: http://llvm.org/viewvc/llvm-project?rev=220162&view=rev
Log:
InstCombine: Optimize icmp eq/ne (shl Const2, A), Const1
The following implements the optimization for sequences of the form:
icmp eq/ne (shl Const2, A), Const1
Such sequences can be transformed to:
icmp eq/ne A, (TrailingZeros(Const1) - TrailingZeros(Const2))
This handles only the equality operators for now. Other operators need
to be handled.
Patch by Ankur Garg!
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombine.h
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/trunk/test/Transforms/InstCombine/icmp.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombine.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombine.h?rev=220162&r1=220161&r2=220162&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombine.h (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombine.h Sun Oct 19 03:23:08 2014
@@ -191,6 +191,8 @@ public:
ConstantInt *DivRHS);
Instruction *FoldICmpCstShrCst(ICmpInst &I, Value *Op, Value *A,
ConstantInt *CI1, ConstantInt *CI2);
+ Instruction *FoldICmpCstShlCst(ICmpInst &I, Value *Op, Value *A,
+ ConstantInt *CI1, ConstantInt *CI2);
Instruction *FoldICmpAddOpCst(Instruction &ICI, Value *X, ConstantInt *CI,
ICmpInst::Predicate Pred);
Instruction *FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=220162&r1=220161&r2=220162&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Sun Oct 19 03:23:08 2014
@@ -1119,6 +1119,49 @@ Instruction *InstCombiner::FoldICmpCstSh
return getConstant(false);
}
+/// FoldICmpCstShlCst - Handle "(icmp eq/ne (shl const2, A), const1)" ->
+/// (icmp eq/ne A, TrailingZeros(const1) - TrailingZeros(const2)).
+Instruction *InstCombiner::FoldICmpCstShlCst(ICmpInst &I, Value *Op, Value *A,
+ ConstantInt *CI1,
+ ConstantInt *CI2) {
+ assert(I.isEquality() && "Cannot fold icmp gt/lt");
+
+ auto getConstant = [&I, this](bool IsTrue) {
+ if (I.getPredicate() == I.ICMP_NE)
+ IsTrue = !IsTrue;
+ return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), IsTrue));
+ };
+
+ auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
+ if (I.getPredicate() == I.ICMP_NE)
+ Pred = CmpInst::getInversePredicate(Pred);
+ return new ICmpInst(Pred, LHS, RHS);
+ };
+
+ APInt AP1 = CI1->getValue();
+ APInt AP2 = CI2->getValue();
+
+ assert(AP2 != 0 && "Handled in InstSimplify");
+
+ unsigned AP2TrailingZeros = AP2.countTrailingZeros();
+
+ if (!AP1 && AP2TrailingZeros != 0)
+ return getICmp(I.ICMP_UGE, A,
+ ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
+
+ if (AP1 == AP2)
+ return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
+
+ // Get the distance between the lowest bits that are set.
+ int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
+
+ if (Shift > 0 && AP2.shl(Shift) == AP1)
+ return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
+
+ // Shifting const2 will never be equal to const1.
+ return getConstant(false);
+}
+
/// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)".
///
Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
@@ -2575,13 +2618,17 @@ Instruction *InstCombiner::visitICmpInst
Builder->getInt(CI->getValue()-1));
}
- // (icmp eq/ne (ashr/lshr const2, A), const1)
if (I.isEquality()) {
ConstantInt *CI2;
if (match(Op0, m_AShr(m_ConstantInt(CI2), m_Value(A))) ||
match(Op0, m_LShr(m_ConstantInt(CI2), m_Value(A)))) {
+ // (icmp eq/ne (ashr/lshr const2, A), const1)
return FoldICmpCstShrCst(I, Op0, A, CI, CI2);
}
+ if (match(Op0, m_Shl(m_ConstantInt(CI2), m_Value(A)))) {
+ // (icmp eq/ne (shl const2, A), const1)
+ return FoldICmpCstShlCst(I, Op0, A, CI, CI2);
+ }
}
// If this comparison is a normal comparison, it demands all
Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=220162&r1=220161&r2=220162&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Sun Oct 19 03:23:08 2014
@@ -1418,3 +1418,64 @@ define i1 @icmp_and_or_lshr_cst(i32 %x)
%ret = icmp ne i32 %and, 0
ret i1 %ret
}
+
+; CHECK-LABEL: @shl_ap1_zero_ap2_non_zero_2
+; CHECK-NEXT: %cmp = icmp ugt i32 %a, 29
+; CHECK-NEXT: ret i1 %cmp
+define i1 @shl_ap1_zero_ap2_non_zero_2(i32 %a) {
+ %shl = shl i32 4, %a
+ %cmp = icmp eq i32 %shl, 0
+ ret i1 %cmp
+}
+
+; CHECK-LABEL: @shl_ap1_zero_ap2_non_zero_4
+; CHECK-NEXT: %cmp = icmp ugt i32 %a, 30
+; CHECK-NEXT: ret i1 %cmp
+define i1 @shl_ap1_zero_ap2_non_zero_4(i32 %a) {
+ %shl = shl i32 -2, %a
+ %cmp = icmp eq i32 %shl, 0
+ ret i1 %cmp
+}
+
+; CHECK-LABEL: @shl_ap1_non_zero_ap2_non_zero_both_positive
+; CHECK-NEXT: %cmp = icmp eq i32 %a, 0
+; CHECK-NEXT: ret i1 %cmp
+define i1 @shl_ap1_non_zero_ap2_non_zero_both_positive(i32 %a) {
+ %shl = shl i32 50, %a
+ %cmp = icmp eq i32 %shl, 50
+ ret i1 %cmp
+}
+
+; CHECK-LABEL: @shl_ap1_non_zero_ap2_non_zero_both_negative
+; CHECK-NEXT: %cmp = icmp eq i32 %a, 0
+; CHECK-NEXT: ret i1 %cmp
+define i1 @shl_ap1_non_zero_ap2_non_zero_both_negative(i32 %a) {
+ %shl = shl i32 -50, %a
+ %cmp = icmp eq i32 %shl, -50
+ ret i1 %cmp
+}
+
+; CHECK-LABEL: @shl_ap1_non_zero_ap2_non_zero_ap1_1
+; CHECK-NEXT: ret i1 false
+define i1 @shl_ap1_non_zero_ap2_non_zero_ap1_1(i32 %a) {
+ %shl = shl i32 50, %a
+ %cmp = icmp eq i32 %shl, 25
+ ret i1 %cmp
+}
+
+; CHECK-LABEL: @shl_ap1_non_zero_ap2_non_zero_ap1_2
+; CHECK-NEXT: %cmp = icmp eq i32 %a, 1
+; CHECK-NEXT: ret i1 %cmp
+define i1 @shl_ap1_non_zero_ap2_non_zero_ap1_2(i32 %a) {
+ %shl = shl i32 25, %a
+ %cmp = icmp eq i32 %shl, 50
+ ret i1 %cmp
+}
+
+; CHECK-LABEL: @shl_ap1_non_zero_ap2_non_zero_ap1_3
+; CHECK-NEXT: ret i1 false
+define i1 @shl_ap1_non_zero_ap2_non_zero_ap1_3(i32 %a) {
+ %shl = shl i32 26, %a
+ %cmp = icmp eq i32 %shl, 50
+ ret i1 %cmp
+}
More information about the llvm-commits
mailing list