Skip to content

[DAG] Recognise AVGFLOOR (((A >> 1) + (B >> 1)) + (A & B & 1)) patterns #169644

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
RKSimon merged 5 commits into from
Dec 10, 2025
Merged

[DAG] Recognise AVGFLOOR (((A >> 1) + (B >> 1)) + (A & B & 1)) patterns #169644

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
e734202
[DAG] Recognise AVGFLOOR (((A >> 1) + (B >> 1)) + (A & B & 1)) patterns
RKSimon Nov 26, 2025
20bd43c
Merge branch 'main' into dag-avgfloor-reassoc
RKSimon Dec 5, 2025
86db993
Merge branch 'main' into dag-avgfloor-reassoc
RKSimon Dec 9, 2025
6a796d3
Use m_ReassociatableAdd now that #170061 is fixed
RKSimon Dec 9, 2025
e4e559b
Merge branch 'main' into dag-avgfloor-reassoc
RKSimon Dec 10, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
19 changes: 15 additions & 4 deletions llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3160,19 +3160,30 @@ SDValue DAGCombiner::visitADDLike(SDNode *N) {
}

// Attempt to form avgfloor(A, B) from (A & B) + ((A ^ B) >> 1)
// Attempt to form avgfloor(A, B) from ((A >> 1) + (B >> 1)) + (A & B & 1)
SDValue DAGCombiner::foldAddToAvg(SDNode *N, const SDLoc &DL) {
SDValue N0 = N->getOperand(0);
EVT VT = N0.getValueType();
SDValue A, B;

if ((!LegalOperations || hasOperation(ISD::AVGFLOORU, VT)) &&
sd_match(N, m_Add(m_And(m_Value(A), m_Value(B)),
m_Srl(m_Xor(m_Deferred(A), m_Deferred(B)), m_One())))) {
(sd_match(N,
m_Add(m_And(m_Value(A), m_Value(B)),
m_Srl(m_Xor(m_Deferred(A), m_Deferred(B)), m_One()))) ||
sd_match(N, m_ReassociatableAdd(
m_Srl(m_Value(A), m_One()), m_Srl(m_Value(B), m_One()),
m_ReassociatableAnd(m_Deferred(A), m_Deferred(B),
m_One()))))) {
return DAG.getNode(ISD::AVGFLOORU, DL, VT, A, B);
}
if ((!LegalOperations || hasOperation(ISD::AVGFLOORS, VT)) &&
sd_match(N, m_Add(m_And(m_Value(A), m_Value(B)),
m_Sra(m_Xor(m_Deferred(A), m_Deferred(B)), m_One())))) {
(sd_match(N,
m_Add(m_And(m_Value(A), m_Value(B)),
m_Sra(m_Xor(m_Deferred(A), m_Deferred(B)), m_One()))) ||
sd_match(N, m_ReassociatableAdd(
m_Sra(m_Value(A), m_One()), m_Sra(m_Value(B), m_One()),
m_ReassociatableAnd(m_Deferred(A), m_Deferred(B),
m_One()))))) {
return DAG.getNode(ISD::AVGFLOORS, DL, VT, A, B);
}

Expand Down
96 changes: 36 additions & 60 deletions llvm/test/CodeGen/X86/avgfloors-scalar.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -38,26 +38,20 @@ define i8 @test_fixed_i8(i8 %a0, i8 %a1) nounwind {
define i8 @test_lsb_i8(i8 %a0, i8 %a1) nounwind {
; X86-LABEL: test_lsb_i8:
; X86: # %bb.0:
; X86-NEXT: movzbl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movzbl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl %eax, %edx
; X86-NEXT: sarb %dl
; X86-NEXT: andb %cl, %al
; X86-NEXT: sarb %cl
; X86-NEXT: addb %dl, %cl
; X86-NEXT: andb $1, %al
; X86-NEXT: addb %cl, %al
; X86-NEXT: movsbl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movsbl {{[0-9]+}}(%esp), %eax
; X86-NEXT: addl %ecx, %eax
; X86-NEXT: shrl %eax
; X86-NEXT: # kill: def $al killed $al killed $eax
; X86-NEXT: retl
;
; X64-LABEL: test_lsb_i8:
; X64: # %bb.0:
; X64-NEXT: movl %edi, %eax
; X64-NEXT: sarb %al
; X64-NEXT: andb %sil, %dil
; X64-NEXT: sarb %sil
; X64-NEXT: addb %sil, %al
; X64-NEXT: andb $1, %dil
; X64-NEXT: addb %dil, %al
; X64-NEXT: movsbl %sil, %ecx
; X64-NEXT: movsbl %dil, %eax
; X64-NEXT: addl %ecx, %eax
; X64-NEXT: shrl %eax
; X64-NEXT: # kill: def $al killed $al killed $eax
; X64-NEXT: retq
%s0 = ashr i8 %a0, 1
%s1 = ashr i8 %a1, 1
Expand Down Expand Up @@ -124,26 +118,17 @@ define i16 @test_lsb_i16(i16 %a0, i16 %a1) nounwind {
; X86: # %bb.0:
; X86-NEXT: movswl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movswl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl %eax, %edx
; X86-NEXT: sarl %edx
; X86-NEXT: andl %ecx, %eax
; X86-NEXT: sarl %ecx
; X86-NEXT: addl %edx, %ecx
; X86-NEXT: andl $1, %eax
; X86-NEXT: addl %ecx, %eax
; X86-NEXT: shrl %eax
; X86-NEXT: # kill: def $ax killed $ax killed $eax
; X86-NEXT: retl
;
; X64-LABEL: test_lsb_i16:
; X64: # %bb.0:
; X64-NEXT: movswl %si, %eax
; X64-NEXT: movswl %di, %ecx
; X64-NEXT: sarl %ecx
; X64-NEXT: sarl %eax
; X64-NEXT: movswl %si, %ecx
; X64-NEXT: movswl %di, %eax
; X64-NEXT: addl %ecx, %eax
; X64-NEXT: andl %esi, %edi
; X64-NEXT: andl $1, %edi
; X64-NEXT: addl %edi, %eax
; X64-NEXT: shrl %eax
; X64-NEXT: # kill: def $ax killed $ax killed $eax
; X64-NEXT: retq
%s0 = ashr i16 %a0, 1
Expand Down Expand Up @@ -214,23 +199,19 @@ define i32 @test_lsb_i32(i32 %a0, i32 %a1) nounwind {
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl %eax, %edx
; X86-NEXT: sarl %edx
; X86-NEXT: andl %ecx, %eax
; X86-NEXT: sarl %ecx
; X86-NEXT: addl %edx, %ecx
; X86-NEXT: andl $1, %eax
; X86-NEXT: addl %ecx, %eax
; X86-NEXT: andl %ecx, %edx
; X86-NEXT: xorl %ecx, %eax
; X86-NEXT: sarl %eax
; X86-NEXT: addl %edx, %eax
; X86-NEXT: retl
;
; X64-LABEL: test_lsb_i32:
; X64: # %bb.0:
; X64-NEXT: movl %edi, %eax
; X64-NEXT: sarl %eax
; X64-NEXT: andl %esi, %edi
; X64-NEXT: sarl %esi
; X64-NEXT: addl %esi, %eax
; X64-NEXT: andl $1, %edi
; X64-NEXT: addl %edi, %eax
; X64-NEXT: movslq %esi, %rcx
; X64-NEXT: movslq %edi, %rax
; X64-NEXT: addq %rcx, %rax
; X64-NEXT: shrq %rax
; X64-NEXT: # kill: def $eax killed $eax killed $rax
; X64-NEXT: retq
%s0 = ashr i32 %a0, 1
%s1 = ashr i32 %a1, 1
Expand Down Expand Up @@ -316,36 +297,31 @@ define i64 @test_lsb_i64(i64 %a0, i64 %a1) nounwind {
; X86-NEXT: pushl %edi
; X86-NEXT: pushl %esi
; X86-NEXT: movl {{[0-9]+}}(%esp), %esi
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl {{[0-9]+}}(%esp), %edi
; X86-NEXT: movl %edi, %ebx
; X86-NEXT: sarl %ebx
; X86-NEXT: shldl $31, %eax, %edi
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl %eax, %ebx
; X86-NEXT: xorl %esi, %ebx
; X86-NEXT: movl %ecx, %edx
; X86-NEXT: xorl %edi, %edx
; X86-NEXT: shrdl $1, %edx, %ebx
; X86-NEXT: andl %edi, %ecx
; X86-NEXT: sarl %edx
; X86-NEXT: shldl $31, %esi, %ecx
; X86-NEXT: addl %edi, %ecx
; X86-NEXT: adcl %ebx, %edx
; X86-NEXT: andl %esi, %eax
; X86-NEXT: andl $1, %eax
; X86-NEXT: addl %ecx, %eax
; X86-NEXT: adcl $0, %edx
; X86-NEXT: addl %ebx, %eax
; X86-NEXT: adcl %ecx, %edx
; X86-NEXT: popl %esi
; X86-NEXT: popl %edi
; X86-NEXT: popl %ebx
; X86-NEXT: retl
;
; X64-LABEL: test_lsb_i64:
; X64: # %bb.0:
; X64-NEXT: movq %rdi, %rcx
; X64-NEXT: sarq %rcx
; X64-NEXT: andl %esi, %edi
; X64-NEXT: movq %rsi, %rax
; X64-NEXT: sarq %rax
; X64-NEXT: addq %rcx, %rax
; X64-NEXT: andl $1, %edi
; X64-NEXT: addq %rdi, %rax
; X64-NEXT: andq %rdi, %rax
; X64-NEXT: xorq %rdi, %rsi
; X64-NEXT: sarq %rsi
; X64-NEXT: addq %rsi, %rax
; X64-NEXT: retq
%s0 = ashr i64 %a0, 1
%s1 = ashr i64 %a1, 1
Expand Down
96 changes: 30 additions & 66 deletions llvm/test/CodeGen/X86/avgflooru-scalar.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -40,24 +40,18 @@ define i8 @test_lsb_i8(i8 %a0, i8 %a1) nounwind {
; X86: # %bb.0:
; X86-NEXT: movzbl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movzbl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl %eax, %edx
; X86-NEXT: shrb %dl
; X86-NEXT: andb %cl, %al
; X86-NEXT: shrb %cl
; X86-NEXT: addb %dl, %cl
; X86-NEXT: andb $1, %al
; X86-NEXT: addb %cl, %al
; X86-NEXT: addl %ecx, %eax
; X86-NEXT: shrl %eax
; X86-NEXT: # kill: def $al killed $al killed $eax
; X86-NEXT: retl
;
; X64-LABEL: test_lsb_i8:
; X64: # %bb.0:
; X64-NEXT: movl %edi, %eax
; X64-NEXT: shrb %al
; X64-NEXT: andb %sil, %dil
; X64-NEXT: shrb %sil
; X64-NEXT: addb %sil, %al
; X64-NEXT: andb $1, %dil
; X64-NEXT: addb %dil, %al
; X64-NEXT: movzbl %sil, %ecx
; X64-NEXT: movzbl %dil, %eax
; X64-NEXT: addl %ecx, %eax
; X64-NEXT: shrl %eax
; X64-NEXT: # kill: def $al killed $al killed $eax
; X64-NEXT: retq
%s0 = lshr i8 %a0, 1
%s1 = lshr i8 %a1, 1
Expand Down Expand Up @@ -124,26 +118,17 @@ define i16 @test_lsb_i16(i16 %a0, i16 %a1) nounwind {
; X86: # %bb.0:
; X86-NEXT: movzwl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movzwl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl %eax, %edx
; X86-NEXT: shrl %edx
; X86-NEXT: andl %ecx, %eax
; X86-NEXT: shrl %ecx
; X86-NEXT: addl %edx, %ecx
; X86-NEXT: andl $1, %eax
; X86-NEXT: addl %ecx, %eax
; X86-NEXT: shrl %eax
; X86-NEXT: # kill: def $ax killed $ax killed $eax
; X86-NEXT: retl
;
; X64-LABEL: test_lsb_i16:
; X64: # %bb.0:
; X64-NEXT: movzwl %si, %eax
; X64-NEXT: movzwl %di, %ecx
; X64-NEXT: shrl %ecx
; X64-NEXT: shrl %eax
; X64-NEXT: movzwl %si, %ecx
; X64-NEXT: movzwl %di, %eax
; X64-NEXT: addl %ecx, %eax
; X64-NEXT: andl %esi, %edi
; X64-NEXT: andl $1, %edi
; X64-NEXT: addl %edi, %eax
; X64-NEXT: shrl %eax
; X64-NEXT: # kill: def $ax killed $ax killed $eax
; X64-NEXT: retq
%s0 = lshr i16 %a0, 1
Expand Down Expand Up @@ -214,23 +199,19 @@ define i32 @test_lsb_i32(i32 %a0, i32 %a1) nounwind {
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl %eax, %edx
; X86-NEXT: shrl %edx
; X86-NEXT: andl %ecx, %eax
; X86-NEXT: shrl %ecx
; X86-NEXT: addl %edx, %ecx
; X86-NEXT: andl $1, %eax
; X86-NEXT: addl %ecx, %eax
; X86-NEXT: andl %ecx, %edx
; X86-NEXT: xorl %ecx, %eax
; X86-NEXT: shrl %eax
; X86-NEXT: addl %edx, %eax
; X86-NEXT: retl
;
; X64-LABEL: test_lsb_i32:
; X64: # %bb.0:
; X64-NEXT: movl %esi, %ecx
; X64-NEXT: movl %edi, %eax
; X64-NEXT: shrl %eax
; X64-NEXT: andl %esi, %edi
; X64-NEXT: shrl %esi
; X64-NEXT: addl %esi, %eax
; X64-NEXT: andl $1, %edi
; X64-NEXT: addl %edi, %eax
; X64-NEXT: addq %rcx, %rax
; X64-NEXT: shrq %rax
; X64-NEXT: # kill: def $eax killed $eax killed $rax
; X64-NEXT: retq
%s0 = lshr i32 %a0, 1
%s1 = lshr i32 %a1, 1
Expand Down Expand Up @@ -300,40 +281,23 @@ define i64 @test_fixed_i64(i64 %a0, i64 %a1) nounwind {
define i64 @test_lsb_i64(i64 %a0, i64 %a1) nounwind {
; X86-LABEL: test_lsb_i64:
; X86: # %bb.0:
; X86-NEXT: pushl %ebx
; X86-NEXT: pushl %edi
; X86-NEXT: pushl %esi
; X86-NEXT: movl {{[0-9]+}}(%esp), %esi
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl {{[0-9]+}}(%esp), %edi
; X86-NEXT: movl %edi, %ebx
; X86-NEXT: shrl %ebx
; X86-NEXT: shldl $31, %eax, %edi
; X86-NEXT: movl %ecx, %edx
; X86-NEXT: shrl %edx
; X86-NEXT: shldl $31, %esi, %ecx
; X86-NEXT: addl %edi, %ecx
; X86-NEXT: adcl %ebx, %edx
; X86-NEXT: andl %esi, %eax
; X86-NEXT: andl $1, %eax
; X86-NEXT: addl %ecx, %eax
; X86-NEXT: adcl $0, %edx
; X86-NEXT: popl %esi
; X86-NEXT: popl %edi
; X86-NEXT: popl %ebx
; X86-NEXT: addl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: adcl {{[0-9]+}}(%esp), %eax
; X86-NEXT: setb %dl
; X86-NEXT: movzbl %dl, %edx
; X86-NEXT: shldl $31, %eax, %edx
; X86-NEXT: shldl $31, %ecx, %eax
; X86-NEXT: retl
;
; X64-LABEL: test_lsb_i64:
; X64: # %bb.0:
; X64-NEXT: movq %rdi, %rcx
; X64-NEXT: shrq %rcx
; X64-NEXT: andl %esi, %edi
; X64-NEXT: movq %rsi, %rax
; X64-NEXT: shrq %rax
; X64-NEXT: addq %rcx, %rax
; X64-NEXT: andl $1, %edi
; X64-NEXT: addq %rdi, %rax
; X64-NEXT: andq %rdi, %rax
; X64-NEXT: xorq %rdi, %rsi
; X64-NEXT: shrq %rsi
; X64-NEXT: addq %rsi, %rax
; X64-NEXT: retq
%s0 = lshr i64 %a0, 1
%s1 = lshr i64 %a1, 1
Expand Down
Loading