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[X86] ICMP EQ/NE MIN_SIGNED_INT - avoid immediate argument by using NEG + SETO/SETNO #94948

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Merged
merged 2 commits into from
Jun 11, 2024
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[X86] ICMP EQ/NE MIN_SIGNED_INT - avoid immediate argument by using NEG + SETO/SETNO #94948

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c8af776
[X86] ICMP EQ/NE MIN_SIGNED_INT - avoid immediate argument by using N…
RKSimon Jun 10, 2024
fedeaba
[X86] Limit i8/i16 eq/ne MIN_SIGNED_INT to one use only
RKSimon Jun 11, 2024
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14 changes: 14 additions & 0 deletions llvm/lib/Target/X86/X86ISelLowering.cpp
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Expand Up @@ -23816,6 +23816,20 @@ SDValue X86TargetLowering::emitFlagsForSetcc(SDValue Op0, SDValue Op1,
}
}

// Look for X == INT_MIN or X != INT_MIN. We can use NEG and test for
// overflow.
if (isMinSignedConstant(Op1)) {
EVT VT = Op0.getValueType();
if (VT == MVT::i32 || VT == MVT::i64 || Op0->hasOneUse()) {
SDVTList CmpVTs = DAG.getVTList(VT, MVT::i32);
X86::CondCode CondCode = CC == ISD::SETEQ ? X86::COND_O : X86::COND_NO;
X86CC = DAG.getTargetConstant(CondCode, dl, MVT::i8);
SDValue Neg = DAG.getNode(X86ISD::SUB, dl, CmpVTs,
DAG.getConstant(0, dl, VT), Op0);
return SDValue(Neg.getNode(), 1);
}
}

// Try to use the carry flag from the add in place of an separate CMP for:
// (seteq (add X, -1), -1). Similar for setne.
if (isAllOnesConstant(Op1) && Op0.getOpcode() == ISD::ADD &&
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4 changes: 2 additions & 2 deletions llvm/test/CodeGen/X86/2008-06-16-SubregsBug.ll
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Expand Up @@ -8,8 +8,8 @@ define i16 @test(ptr %tmp179) nounwind {
; CHECK-NEXT: movzwl (%eax), %eax
; CHECK-NEXT: movl %eax, %ecx
; CHECK-NEXT: andl $64512, %ecx ## imm = 0xFC00
; CHECK-NEXT: cmpl $32768, %ecx ## imm = 0x8000
; CHECK-NEXT: jne LBB0_2
; CHECK-NEXT: negw %cx
; CHECK-NEXT: jno LBB0_2
; CHECK-NEXT: ## %bb.1: ## %bb189
; CHECK-NEXT: ## kill: def $ax killed $ax killed $eax
; CHECK-NEXT: retl
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13 changes: 3 additions & 10 deletions llvm/test/CodeGen/X86/abs.ll
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Expand Up @@ -783,8 +783,7 @@ define i32 @test_minsigned_i32(i32 %a0, i32 %a1) nounwind {
; X64-NEXT: movl %edi, %eax
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I think this will increase register pressure. Should we check one use of it?

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I've been testing with hasOneUse but it isn't great as its purely down to final execution order - the abs tests can reuse the neg flag results in most cases. I'm going to see if X86FlagsCopyLowering can help us

; X64-NEXT: negl %eax
; X64-NEXT: cmovsl %edi, %eax
; X64-NEXT: cmpl $-2147483648, %edi # imm = 0x80000000
; X64-NEXT: cmovel %esi, %eax
; X64-NEXT: cmovol %esi, %eax
; X64-NEXT: retq
;
; X86-LABEL: test_minsigned_i32:
Expand All @@ -793,11 +792,7 @@ define i32 @test_minsigned_i32(i32 %a0, i32 %a1) nounwind {
; X86-NEXT: movl %ecx, %eax
; X86-NEXT: negl %eax
; X86-NEXT: cmovsl %ecx, %eax
; X86-NEXT: cmpl $-2147483648, %ecx # imm = 0x80000000
; X86-NEXT: jne .LBB19_2
; X86-NEXT: # %bb.1:
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: .LBB19_2:
; X86-NEXT: cmovol {{[0-9]+}}(%esp), %eax
; X86-NEXT: retl
%lim = icmp eq i32 %a0, -2147483648
%abs = tail call i32 @llvm.abs.i32(i32 %a0, i1 false)
Expand All @@ -811,9 +806,7 @@ define i64 @test_minsigned_i64(i64 %a0, i64 %a1) nounwind {
; X64-NEXT: movq %rdi, %rax
; X64-NEXT: negq %rax
; X64-NEXT: cmovsq %rdi, %rax
; X64-NEXT: movabsq $-9223372036854775808, %rcx # imm = 0x8000000000000000
; X64-NEXT: cmpq %rcx, %rdi
; X64-NEXT: cmoveq %rsi, %rax
; X64-NEXT: cmovoq %rsi, %rax
; X64-NEXT: retq
;
; X86-LABEL: test_minsigned_i64:
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4 changes: 2 additions & 2 deletions llvm/test/CodeGen/X86/combine-sdiv.ll
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Expand Up @@ -58,8 +58,8 @@ define i32 @combine_sdiv_by_minsigned(i32 %x) {
; CHECK-LABEL: combine_sdiv_by_minsigned:
; CHECK: # %bb.0:
; CHECK-NEXT: xorl %eax, %eax
; CHECK-NEXT: cmpl $-2147483648, %edi # imm = 0x80000000
; CHECK-NEXT: sete %al
; CHECK-NEXT: negl %edi
; CHECK-NEXT: seto %al
; CHECK-NEXT: retq
%1 = sdiv i32 %x, -2147483648
ret i32 %1
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18 changes: 10 additions & 8 deletions llvm/test/CodeGen/X86/is_fpclass.ll
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Expand Up @@ -937,15 +937,16 @@ entry:
define i1 @is_minus_zero_f(float %x) {
; X86-LABEL: is_minus_zero_f:
; X86: # %bb.0: # %entry
; X86-NEXT: cmpl $-2147483648, {{[0-9]+}}(%esp) # imm = 0x80000000
; X86-NEXT: sete %al
; X86-NEXT: xorl %eax, %eax
; X86-NEXT: cmpl {{[0-9]+}}(%esp), %eax
; X86-NEXT: seto %al
; X86-NEXT: retl
;
; X64-LABEL: is_minus_zero_f:
; X64: # %bb.0: # %entry
; X64-NEXT: movd %xmm0, %eax
; X64-NEXT: cmpl $-2147483648, %eax # imm = 0x80000000
; X64-NEXT: sete %al
; X64-NEXT: negl %eax
; X64-NEXT: seto %al
; X64-NEXT: retq
entry:
%0 = tail call i1 @llvm.is.fpclass.f32(float %x, i32 32) ; 0x20 = "-zero"
Expand All @@ -955,15 +956,16 @@ entry:
define i1 @not_is_minus_zero_f(float %x) {
; X86-LABEL: not_is_minus_zero_f:
; X86: # %bb.0: # %entry
; X86-NEXT: cmpl $-2147483648, {{[0-9]+}}(%esp) # imm = 0x80000000
; X86-NEXT: setne %al
; X86-NEXT: xorl %eax, %eax
; X86-NEXT: cmpl {{[0-9]+}}(%esp), %eax
; X86-NEXT: setno %al
; X86-NEXT: retl
;
; X64-LABEL: not_is_minus_zero_f:
; X64: # %bb.0: # %entry
; X64-NEXT: movd %xmm0, %eax
; X64-NEXT: cmpl $-2147483648, %eax # imm = 0x80000000
; X64-NEXT: setne %al
; X64-NEXT: negl %eax
; X64-NEXT: setno %al
; X64-NEXT: retq
entry:
%0 = tail call i1 @llvm.is.fpclass.f32(float %x, i32 991) ; ~0x20 = ~"-zero"
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6 changes: 3 additions & 3 deletions llvm/test/CodeGen/X86/lsr-overflow.ll
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Expand Up @@ -4,9 +4,9 @@
; The comparison uses the pre-inc value, which could lead LSR to
; try to compute -INT64_MIN.

; CHECK: movabsq $-9223372036854775808, %rax
; CHECK: cmpq %rax,
; CHECK: sete %al
; CHECK-NOT: movabsq $-9223372036854775808, %rax
; CHECK: negq %r
; CHECK-NEXT: seto %al

declare i64 @bar()

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4 changes: 2 additions & 2 deletions llvm/test/CodeGen/X86/shrink-compare-pgso.ll
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Expand Up @@ -265,8 +265,8 @@ if.end:
define dso_local void @test_sext_i8_icmp_neg128(i8 %x) nounwind !prof !14 {
; CHECK-LABEL: test_sext_i8_icmp_neg128:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: cmpb $-128, %dil
; CHECK-NEXT: je bar # TAILCALL
; CHECK-NEXT: negb %dil
; CHECK-NEXT: jo bar # TAILCALL
; CHECK-NEXT: # %bb.1: # %if.end
; CHECK-NEXT: retq
entry:
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4 changes: 2 additions & 2 deletions llvm/test/CodeGen/X86/shrink-compare.ll
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Expand Up @@ -265,8 +265,8 @@ if.end:
define dso_local void @test_sext_i8_icmp_neg128(i8 %x) nounwind minsize {
; CHECK-LABEL: test_sext_i8_icmp_neg128:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: cmpb $-128, %dil
; CHECK-NEXT: je bar # TAILCALL
; CHECK-NEXT: negb %dil
; CHECK-NEXT: jo bar # TAILCALL
; CHECK-NEXT: # %bb.1: # %if.end
; CHECK-NEXT: retq
entry:
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