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[DAGCombiner] Recognize another rotation idiom

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This is the new idiom:

  x<<(y&31) | x>>((0-y)&31)

which is recognized as:

  x ROTL (y&31)

The change refines matchRotateSub.  In
Neg & (OpSize - 1) == (OpSize - Pos) & (OpSize - 1), if Pos is
Pos' & (OpSize - 1) we can just use Pos' instead of Pos.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203315 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Adam Nemet 2014-03-07 23:56:28 +00:00
parent 622f350944
commit 316d3e3085
2 changed files with 134 additions and 0 deletions
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8
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -3466,6 +3466,14 @@ static bool matchRotateSub(SDValue Pos, SDValue Neg, unsigned OpSize) {
return 0;
SDValue NegOp1 = Neg.getOperand(1);
// On the RHS of [A], if Pos is Pos' & (OpSize - 1), just replace Pos with
// Pos'. The truncation is redundant for the purpose of the equality.
if (MaskLoBits &&
Pos.getOpcode() == ISD::AND &&
Pos.getOperand(1).getOpcode() == ISD::Constant &&
cast<ConstantSDNode>(Pos.getOperand(1))->getAPIntValue() == OpSize - 1)
Pos = Pos.getOperand(0);
// The condition we need is now:
//
// (NegC - NegOp1) & Mask == (OpSize - Pos) & Mask

126
test/CodeGen/X86/rotate4.ll Normal file
View File

@ -0,0 +1,126 @@
; RUN: llc < %s -mtriple=x86_64-apple-darwin -mcpu=generic | FileCheck %s
; Check that we recognize this idiom for rotation too:
; a << (b & 31) | a >> ((0 - b) & 31)
define i32 @rotate_left_32(i32 %a, i32 %b) {
; CHECK-LABEL: rotate_left_32:
; CHECK: roll
entry:
%and = and i32 %b, 31
%shl = shl i32 %a, %and
%0 = sub i32 0, %b
%and3 = and i32 %0, 31
%shr = lshr i32 %a, %and3
%or = or i32 %shl, %shr
ret i32 %or
}
define i32 @rotate_right_32(i32 %a, i32 %b) {
; CHECK-LABEL: rotate_right_32:
; CHECK: rorl
entry:
%and = and i32 %b, 31
%shl = lshr i32 %a, %and
%0 = sub i32 0, %b
%and3 = and i32 %0, 31
%shr = shl i32 %a, %and3
%or = or i32 %shl, %shr
ret i32 %or
}
define i64 @rotate_left_64(i64 %a, i64 %b) {
; CHECK-LABEL: rotate_left_64:
; CHECK: rolq
entry:
%and = and i64 %b, 63
%shl = shl i64 %a, %and
%0 = sub i64 0, %b
%and3 = and i64 %0, 63
%shr = lshr i64 %a, %and3
%or = or i64 %shl, %shr
ret i64 %or
}
define i64 @rotate_right_64(i64 %a, i64 %b) {
; CHECK-LABEL: rotate_right_64:
; CHECK: rorq
entry:
%and = and i64 %b, 63
%shl = lshr i64 %a, %and
%0 = sub i64 0, %b
%and3 = and i64 %0, 63
%shr = shl i64 %a, %and3
%or = or i64 %shl, %shr
ret i64 %or
}
; Also check mem operand.
define void @rotate_left_m32(i32 *%pa, i32 %b) {
; CHECK-LABEL: rotate_left_m32:
; CHECK: roll
; no store:
; CHECK-NOT: mov
entry:
%a = load i32* %pa, align 16
%and = and i32 %b, 31
%shl = shl i32 %a, %and
%0 = sub i32 0, %b
%and3 = and i32 %0, 31
%shr = lshr i32 %a, %and3
%or = or i32 %shl, %shr
store i32 %or, i32* %pa, align 32
ret void
}
define void @rotate_right_m32(i32 *%pa, i32 %b) {
; CHECK-LABEL: rotate_right_m32:
; CHECK: rorl
; no store:
; CHECK-NOT: mov
entry:
%a = load i32* %pa, align 16
%and = and i32 %b, 31
%shl = lshr i32 %a, %and
%0 = sub i32 0, %b
%and3 = and i32 %0, 31
%shr = shl i32 %a, %and3
%or = or i32 %shl, %shr
store i32 %or, i32* %pa, align 32
ret void
}
define void @rotate_left_m64(i64 *%pa, i64 %b) {
; CHECK-LABEL: rotate_left_m64:
; CHECK: rolq
; no store:
; CHECK-NOT: mov
entry:
%a = load i64* %pa, align 16
%and = and i64 %b, 63
%shl = shl i64 %a, %and
%0 = sub i64 0, %b
%and3 = and i64 %0, 63
%shr = lshr i64 %a, %and3
%or = or i64 %shl, %shr
store i64 %or, i64* %pa, align 64
ret void
}
define void @rotate_right_m64(i64 *%pa, i64 %b) {
; CHECK-LABEL: rotate_right_m64:
; CHECK: rorq
; no store:
; CHECK-NOT: mov
entry:
%a = load i64* %pa, align 16
%and = and i64 %b, 63
%shl = lshr i64 %a, %and
%0 = sub i64 0, %b
%and3 = and i64 %0, 63
%shr = shl i64 %a, %and3
%or = or i64 %shl, %shr
store i64 %or, i64* %pa, align 64
ret void
}