[llvm] 34d8c5b - [DAG] Peek through trunc when combining select into shifts.
Amaury Séchet via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 22 17:35:44 PDT 2023
Author: Amaury Séchet
Date: 2023-06-23T00:35:39Z
New Revision: 34d8c5b9ceae5002ae9cd1cbfcb1fd998018bebf
URL: https://github.com/llvm/llvm-project/commit/34d8c5b9ceae5002ae9cd1cbfcb1fd998018bebf
DIFF: https://github.com/llvm/llvm-project/commit/34d8c5b9ceae5002ae9cd1cbfcb1fd998018bebf.diff
LOG: [DAG] Peek through trunc when combining select into shifts.
This fixes a regression in D127115
Depends on D127115
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D151916
Added:
Modified:
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
llvm/test/CodeGen/X86/dagcombine-select.ll
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 3d095b1e681a6..357b0c66a8c4f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2485,6 +2485,17 @@ SDValue DAGCombiner::foldBinOpIntoSelect(SDNode *BO) {
if (Sel.getOpcode() != ISD::SELECT || !Sel.hasOneUse()) {
SelOpNo = 1;
Sel = BO->getOperand(1);
+
+ // Peek through trunc to shift amount type.
+ if ((BinOpcode == ISD::SHL || BinOpcode == ISD::SRA ||
+ BinOpcode == ISD::SRL) && Sel.hasOneUse()) {
+ // This is valid when the truncated bits of x are already zero.
+ SDValue Op;
+ KnownBits Known;
+ if (isTruncateOf(DAG, Sel, Op, Known) &&
+ Known.countMaxActiveBits() < Sel.getScalarValueSizeInBits())
+ Sel = Op;
+ }
}
if (Sel.getOpcode() != ISD::SELECT || !Sel.hasOneUse())
diff --git a/llvm/test/CodeGen/X86/dagcombine-select.ll b/llvm/test/CodeGen/X86/dagcombine-select.ll
index be9c3977eeb38..d29f161c76fb8 100644
--- a/llvm/test/CodeGen/X86/dagcombine-select.ll
+++ b/llvm/test/CodeGen/X86/dagcombine-select.ll
@@ -194,12 +194,10 @@ define i32 @sel_constants_shl_constant(i1 %cond) {
define i32 @shl_constant_sel_constants(i1 %cond) {
; CHECK-LABEL: shl_constant_sel_constants:
; CHECK: # %bb.0:
-; CHECK-NEXT: movl %edi, %ecx
-; CHECK-NEXT: andb $1, %cl
-; CHECK-NEXT: xorb $3, %cl
-; CHECK-NEXT: movl $1, %eax
-; CHECK-NEXT: # kill: def $cl killed $cl killed $ecx
-; CHECK-NEXT: shll %cl, %eax
+; CHECK-NEXT: notb %dil
+; CHECK-NEXT: movzbl %dil, %eax
+; CHECK-NEXT: andl $1, %eax
+; CHECK-NEXT: leal 4(,%rax,4), %eax
; CHECK-NEXT: retq
%sel = select i1 %cond, i32 2, i32 3
%bo = shl i32 1, %sel
@@ -209,12 +207,10 @@ define i32 @shl_constant_sel_constants(i1 %cond) {
define i32 @shl_constant_sel_setcc(i32 %a) {
; CHECK-LABEL: shl_constant_sel_setcc:
; CHECK: # %bb.0:
-; CHECK-NEXT: movl %edi, %ecx
-; CHECK-NEXT: andb $1, %cl
-; CHECK-NEXT: xorb $3, %cl
-; CHECK-NEXT: movl $1, %eax
-; CHECK-NEXT: # kill: def $cl killed $cl killed $ecx
-; CHECK-NEXT: shll %cl, %eax
+; CHECK-NEXT: xorl %eax, %eax
+; CHECK-NEXT: testb $1, %dil
+; CHECK-NEXT: sete %al
+; CHECK-NEXT: leal 4(,%rax,4), %eax
; CHECK-NEXT: retq
%m = and i32 %a, 1
%cond = icmp ne i32 %m, 0
@@ -226,12 +222,9 @@ define i32 @shl_constant_sel_setcc(i32 %a) {
define i32 @lshr_constant_sel_constants(i1 %cond) {
; CHECK-LABEL: lshr_constant_sel_constants:
; CHECK: # %bb.0:
-; CHECK-NEXT: movl %edi, %ecx
-; CHECK-NEXT: andb $1, %cl
-; CHECK-NEXT: xorb $3, %cl
-; CHECK-NEXT: movl $64, %eax
-; CHECK-NEXT: # kill: def $cl killed $cl killed $ecx
-; CHECK-NEXT: shrl %cl, %eax
+; CHECK-NEXT: # kill: def $edi killed $edi def $rdi
+; CHECK-NEXT: andl $1, %edi
+; CHECK-NEXT: leal 8(,%rdi,8), %eax
; CHECK-NEXT: retq
%sel = select i1 %cond, i32 2, i32 3
%bo = lshr i32 64, %sel
@@ -241,12 +234,9 @@ define i32 @lshr_constant_sel_constants(i1 %cond) {
define i32 @lshr_constant_sel_setcc(i32 %a) {
; CHECK-LABEL: lshr_constant_sel_setcc:
; CHECK: # %bb.0:
-; CHECK-NEXT: movl %edi, %ecx
-; CHECK-NEXT: andb $1, %cl
-; CHECK-NEXT: xorb $3, %cl
-; CHECK-NEXT: movl $64, %eax
-; CHECK-NEXT: # kill: def $cl killed $cl killed $ecx
-; CHECK-NEXT: shrl %cl, %eax
+; CHECK-NEXT: # kill: def $edi killed $edi def $rdi
+; CHECK-NEXT: andl $1, %edi
+; CHECK-NEXT: leal 8(,%rdi,8), %eax
; CHECK-NEXT: retq
%m = and i32 %a, 1
%cond = icmp ne i32 %m, 0
@@ -258,12 +248,10 @@ define i32 @lshr_constant_sel_setcc(i32 %a) {
define i32 @ashr_constant_sel_constants(i1 %cond) {
; CHECK-LABEL: ashr_constant_sel_constants:
; CHECK: # %bb.0:
-; CHECK-NEXT: movl %edi, %ecx
-; CHECK-NEXT: andb $1, %cl
-; CHECK-NEXT: xorb $3, %cl
-; CHECK-NEXT: movl $128, %eax
-; CHECK-NEXT: # kill: def $cl killed $cl killed $ecx
-; CHECK-NEXT: shrl %cl, %eax
+; CHECK-NEXT: # kill: def $edi killed $edi def $rdi
+; CHECK-NEXT: andl $1, %edi
+; CHECK-NEXT: shll $4, %edi
+; CHECK-NEXT: leal 16(%rdi), %eax
; CHECK-NEXT: retq
%sel = select i1 %cond, i32 2, i32 3
%bo = ashr i32 128, %sel
@@ -273,12 +261,10 @@ define i32 @ashr_constant_sel_constants(i1 %cond) {
define i32 @ashr_constant_sel_setcc(i32 %a) {
; CHECK-LABEL: ashr_constant_sel_setcc:
; CHECK: # %bb.0:
-; CHECK-NEXT: movl %edi, %ecx
-; CHECK-NEXT: andb $1, %cl
-; CHECK-NEXT: xorb $3, %cl
-; CHECK-NEXT: movl $128, %eax
-; CHECK-NEXT: # kill: def $cl killed $cl killed $ecx
-; CHECK-NEXT: shrl %cl, %eax
+; CHECK-NEXT: # kill: def $edi killed $edi def $rdi
+; CHECK-NEXT: andl $1, %edi
+; CHECK-NEXT: shll $4, %edi
+; CHECK-NEXT: leal 16(%rdi), %eax
; CHECK-NEXT: retq
%m = and i32 %a, 1
%cond = icmp ne i32 %m, 0
More information about the llvm-commits
mailing list