[llvm] [SelectionDAG] Add MaskedValueIsZero check to allow folding of zero extended variables we know are safe to extend (PR #85573)
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Tue Mar 19 07:04:47 PDT 2024
https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/85573
>From e23138c76c236ff18e789570c2a70161f54932b5 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Sun, 17 Mar 2024 14:04:52 -0400
Subject: [PATCH 1/2] [SelectionDAG] Pre-commit tests (NFC)
---
llvm/test/CodeGen/X86/dagcombine-shifts.ll | 134 +++++++++++++++++++++
1 file changed, 134 insertions(+)
diff --git a/llvm/test/CodeGen/X86/dagcombine-shifts.ll b/llvm/test/CodeGen/X86/dagcombine-shifts.ll
index 42b325dd4c229e..229b2a22c0e5af 100644
--- a/llvm/test/CodeGen/X86/dagcombine-shifts.ll
+++ b/llvm/test/CodeGen/X86/dagcombine-shifts.ll
@@ -322,5 +322,139 @@ define void @g(i32 %a) nounwind {
ret void
}
+define i32 @shift_zext_shl(i8 zeroext %x) {
+; X86-LABEL: shift_zext_shl:
+; X86: # %bb.0:
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: andb $64, %al
+; X86-NEXT: movzbl %al, %eax
+; X86-NEXT: shll $9, %eax
+; X86-NEXT: movzwl %ax, %eax
+; X86-NEXT: retl
+;
+; X64-LABEL: shift_zext_shl:
+; X64: # %bb.0:
+; X64-NEXT: andb $64, %dil
+; X64-NEXT: movzbl %dil, %eax
+; X64-NEXT: shll $9, %eax
+; X64-NEXT: movzwl %ax, %eax
+; X64-NEXT: retq
+ %a = and i8 %x, 64
+ %b = zext i8 %a to i16
+ %c = shl i16 %b, 9
+ %d = zext i16 %c to i32
+ ret i32 %d
+}
+
+define i32 @shift_zext_shl2(i8 zeroext %x) {
+; X86-LABEL: shift_zext_shl2:
+; X86: # %bb.0:
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: andl $64, %eax
+; X86-NEXT: shll $9, %eax
+; X86-NEXT: retl
+;
+; X64-LABEL: shift_zext_shl2:
+; X64: # %bb.0:
+; X64-NEXT: movl %edi, %eax
+; X64-NEXT: andl $64, %eax
+; X64-NEXT: shll $9, %eax
+; X64-NEXT: retq
+ %a = and i8 %x, 64
+ %b = zext i8 %a to i32
+ %c = shl i32 %b, 9
+ ret i32 %c
+}
+
+define <4 x i32> @shift_zext_shl_vec(<4 x i8> %x) nounwind {
+; X86-LABEL: shift_zext_shl_vec:
+; X86: # %bb.0:
+; X86-NEXT: pushl %ebx
+; X86-NEXT: pushl %edi
+; X86-NEXT: pushl %esi
+; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %esi
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %edx
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %ebx
+; X86-NEXT: andb $64, %bl
+; X86-NEXT: movzbl %bl, %edi
+; X86-NEXT: shll $9, %edi
+; X86-NEXT: movzwl %di, %edi
+; X86-NEXT: andl $63, %ecx
+; X86-NEXT: shll $8, %ecx
+; X86-NEXT: andl $31, %edx
+; X86-NEXT: shll $7, %edx
+; X86-NEXT: andl $23, %esi
+; X86-NEXT: shll $6, %esi
+; X86-NEXT: movl %esi, 12(%eax)
+; X86-NEXT: movl %edx, 8(%eax)
+; X86-NEXT: movl %ecx, 4(%eax)
+; X86-NEXT: movl %edi, (%eax)
+; X86-NEXT: popl %esi
+; X86-NEXT: popl %edi
+; X86-NEXT: popl %ebx
+; X86-NEXT: retl $4
+;
+; X64-LABEL: shift_zext_shl_vec:
+; X64: # %bb.0:
+; X64-NEXT: pand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; X64-NEXT: pxor %xmm1, %xmm1
+; X64-NEXT: punpcklbw {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3],xmm0[4],xmm1[4],xmm0[5],xmm1[5],xmm0[6],xmm1[6],xmm0[7],xmm1[7]
+; X64-NEXT: pmullw {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; X64-NEXT: punpcklwd {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3]
+; X64-NEXT: retq
+ %a = and <4 x i8> %x, <i8 64, i8 63, i8 31, i8 23>
+ %b = zext <4 x i8> %a to <4 x i16>
+ %c = shl <4 x i16> %b, <i16 9, i16 8, i16 7, i16 6>
+ %d = zext <4 x i16> %c to <4 x i32>
+ ret <4 x i32> %d
+}
+
+define <4 x i32> @shift_zext_shl2_vec(<4 x i8> %x) nounwind {
+; X86-LABEL: shift_zext_shl2_vec:
+; X86: # %bb.0:
+; X86-NEXT: pushl %edi
+; X86-NEXT: pushl %esi
+; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %edx
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %esi
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %edi
+; X86-NEXT: andl $23, %edi
+; X86-NEXT: andl $31, %esi
+; X86-NEXT: andl $63, %edx
+; X86-NEXT: andl $64, %ecx
+; X86-NEXT: shll $9, %ecx
+; X86-NEXT: shll $8, %edx
+; X86-NEXT: shll $7, %esi
+; X86-NEXT: shll $6, %edi
+; X86-NEXT: movl %edi, 12(%eax)
+; X86-NEXT: movl %esi, 8(%eax)
+; X86-NEXT: movl %edx, 4(%eax)
+; X86-NEXT: movl %ecx, (%eax)
+; X86-NEXT: popl %esi
+; X86-NEXT: popl %edi
+; X86-NEXT: retl $4
+;
+; X64-LABEL: shift_zext_shl2_vec:
+; X64: # %bb.0:
+; X64-NEXT: pand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; X64-NEXT: pxor %xmm1, %xmm1
+; X64-NEXT: punpcklbw {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3],xmm0[4],xmm1[4],xmm0[5],xmm1[5],xmm0[6],xmm1[6],xmm0[7],xmm1[7]
+; X64-NEXT: punpcklwd {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3]
+; X64-NEXT: pshufd {{.*#+}} xmm1 = xmm0[1,1,3,3]
+; X64-NEXT: pmuludq {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; X64-NEXT: pshufd {{.*#+}} xmm0 = xmm0[0,2,2,3]
+; X64-NEXT: pmuludq {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm1
+; X64-NEXT: pshufd {{.*#+}} xmm1 = xmm1[0,2,2,3]
+; X64-NEXT: punpckldq {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1]
+; X64-NEXT: retq
+ %a = and <4 x i8> %x, <i8 64, i8 63, i8 31, i8 23>
+ %b = zext <4 x i8> %a to <4 x i32>
+ %c = shl <4 x i32> %b, <i32 9, i32 8, i32 7, i32 6>
+ ret <4 x i32> %c
+}
+
declare dso_local void @f(i64)
>From a99f2b04d6157de11032cfc854b9b8cff32fb6f7 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Sun, 17 Mar 2024 12:51:41 -0400
Subject: [PATCH 2/2] [SelectionDAG] Add MaskedValueIsZero check to allow
folding of zero extended variables we know are safe to extend
Add ones for every high bit that will cleared.
This will allow us to evaluate variables that have their bits known to see if they have no risk of overflow despite the shift amount being greater than the difference between the two types.
---
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 15 +++++--
llvm/test/CodeGen/X86/dagcombine-shifts.ll | 39 ++++++++-----------
2 files changed, 28 insertions(+), 26 deletions(-)
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index f199625bf67ad3..5603960930f2c5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -13844,11 +13844,20 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
if (N0.getOpcode() == ISD::SHL) {
// If the original shl may be shifting out bits, do not perform this
// transformation.
- // TODO: Add MaskedValueIsZero check.
unsigned KnownZeroBits = ShVal.getValueSizeInBits() -
ShVal.getOperand(0).getValueSizeInBits();
- if (ShAmtC->getAPIntValue().ugt(KnownZeroBits))
- return SDValue();
+ if (ShAmtC->getAPIntValue().ugt(KnownZeroBits)) {
+ // If the shift is too large, then see if we can deduce that the
+ // shift is safe anyway.
+ // Create a mask that has ones for the bits being shifted out.
+ APInt ShiftOutMask = llvm::APInt::getHighBitsSet(
+ ShVal.getValueSizeInBits(),
+ ShAmtC->getAPIntValue().getZExtValue());
+
+ // Check if the bits being shifted out are known to be zero.
+ if (!DAG.MaskedValueIsZero(ShVal, ShiftOutMask))
+ return SDValue();
+ }
}
// Ensure that the shift amount is wide enough for the shifted value.
diff --git a/llvm/test/CodeGen/X86/dagcombine-shifts.ll b/llvm/test/CodeGen/X86/dagcombine-shifts.ll
index 229b2a22c0e5af..734abfe55a4ec4 100644
--- a/llvm/test/CodeGen/X86/dagcombine-shifts.ll
+++ b/llvm/test/CodeGen/X86/dagcombine-shifts.ll
@@ -326,18 +326,15 @@ define i32 @shift_zext_shl(i8 zeroext %x) {
; X86-LABEL: shift_zext_shl:
; X86: # %bb.0:
; X86-NEXT: movzbl {{[0-9]+}}(%esp), %eax
-; X86-NEXT: andb $64, %al
-; X86-NEXT: movzbl %al, %eax
+; X86-NEXT: andl $64, %eax
; X86-NEXT: shll $9, %eax
-; X86-NEXT: movzwl %ax, %eax
; X86-NEXT: retl
;
; X64-LABEL: shift_zext_shl:
; X64: # %bb.0:
-; X64-NEXT: andb $64, %dil
-; X64-NEXT: movzbl %dil, %eax
+; X64-NEXT: movl %edi, %eax
+; X64-NEXT: andl $64, %eax
; X64-NEXT: shll $9, %eax
-; X64-NEXT: movzwl %ax, %eax
; X64-NEXT: retq
%a = and i8 %x, 64
%b = zext i8 %a to i16
@@ -369,31 +366,27 @@ define i32 @shift_zext_shl2(i8 zeroext %x) {
define <4 x i32> @shift_zext_shl_vec(<4 x i8> %x) nounwind {
; X86-LABEL: shift_zext_shl_vec:
; X86: # %bb.0:
-; X86-NEXT: pushl %ebx
; X86-NEXT: pushl %edi
; X86-NEXT: pushl %esi
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: movzbl {{[0-9]+}}(%esp), %edi
; X86-NEXT: movzbl {{[0-9]+}}(%esp), %esi
; X86-NEXT: movzbl {{[0-9]+}}(%esp), %edx
; X86-NEXT: movzbl {{[0-9]+}}(%esp), %ecx
-; X86-NEXT: movzbl {{[0-9]+}}(%esp), %ebx
-; X86-NEXT: andb $64, %bl
-; X86-NEXT: movzbl %bl, %edi
-; X86-NEXT: shll $9, %edi
-; X86-NEXT: movzwl %di, %edi
-; X86-NEXT: andl $63, %ecx
-; X86-NEXT: shll $8, %ecx
-; X86-NEXT: andl $31, %edx
-; X86-NEXT: shll $7, %edx
-; X86-NEXT: andl $23, %esi
-; X86-NEXT: shll $6, %esi
-; X86-NEXT: movl %esi, 12(%eax)
-; X86-NEXT: movl %edx, 8(%eax)
-; X86-NEXT: movl %ecx, 4(%eax)
-; X86-NEXT: movl %edi, (%eax)
+; X86-NEXT: andl $64, %ecx
+; X86-NEXT: shll $9, %ecx
+; X86-NEXT: andl $63, %edx
+; X86-NEXT: shll $8, %edx
+; X86-NEXT: andl $31, %esi
+; X86-NEXT: shll $7, %esi
+; X86-NEXT: andl $23, %edi
+; X86-NEXT: shll $6, %edi
+; X86-NEXT: movl %edi, 12(%eax)
+; X86-NEXT: movl %esi, 8(%eax)
+; X86-NEXT: movl %edx, 4(%eax)
+; X86-NEXT: movl %ecx, (%eax)
; X86-NEXT: popl %esi
; X86-NEXT: popl %edi
-; X86-NEXT: popl %ebx
; X86-NEXT: retl $4
;
; X64-LABEL: shift_zext_shl_vec:
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