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[TargetLowering] Replace Log2_32_Ceil with Log2_32 in SimplifySetCC ctpop combine. 

This combine can look through (trunc (ctpop X)). When doing this
it tries to make sure the trunc doesn't lose any information
from the ctpop. It does this by checking that the truncated type
has more bits that Log2_32_Ceil of the ctpop type. The Ceil is
unnecessary and pessimizes non-power of 2 types.

For example, ctpop of i256 requires 9 bits to represent the max
value of 256. But ctpop of i255 only requires 8 bits to represent
the max result of 255. Log2_32_Ceil of 256 and 255 both return 8
while Log2_32 returns 8 for 256 and 7 for 255

The code with popcnt enabled is a regression for this test case,
but it does match what already happens with i256 truncated to i9.
Since power of 2 is more likely, I don't think it should block
this change.

Differential Revision: https://reviews.llvm.org/D89412
This commit is contained in:
Craig Topper 2020-10-14 10:52:21 -07:00
parent 47f2dc7e5f
commit 50c9f1e11d
2 changed files with 34 additions and 91 deletions
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2
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
View File

@ -3446,7 +3446,7 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
if (CTPOP.hasOneUse() && CTPOP.getOpcode() == ISD::CTPOP &&
(N0 == CTPOP ||
N0.getValueSizeInBits() > Log2_32_Ceil(CTPOP.getValueSizeInBits()))) {
N0.getValueSizeInBits() > Log2_32(CTPOP.getValueSizeInBits()))) {
EVT CTVT = CTPOP.getValueType();
SDValue CTOp = CTPOP.getOperand(0);

123
llvm/test/CodeGen/X86/ctpop-combine.ll
View File

@ -162,96 +162,39 @@ define i32 @ctpop_ne_one(i64 %x) nounwind readnone {
}
define i1 @ctpop_trunc_non_power2(i255 %x) {
; POPCOUNT-LABEL: ctpop_trunc_non_power2:
; POPCOUNT: # %bb.0:
; POPCOUNT-NEXT: movabsq $9223372036854775807, %rax # imm = 0x7FFFFFFFFFFFFFFF
; POPCOUNT-NEXT: andq %rcx, %rax
; POPCOUNT-NEXT: popcntq %rsi, %rcx
; POPCOUNT-NEXT: popcntq %rdi, %rsi
; POPCOUNT-NEXT: addl %ecx, %esi
; POPCOUNT-NEXT: popcntq %rax, %rax
; POPCOUNT-NEXT: popcntq %rdx, %rcx
; POPCOUNT-NEXT: addl %eax, %ecx
; POPCOUNT-NEXT: addl %esi, %ecx
; POPCOUNT-NEXT: cmpb $1, %cl
; POPCOUNT-NEXT: sete %al
; POPCOUNT-NEXT: retq
;
; NO-POPCOUNT-LABEL: ctpop_trunc_non_power2:
; NO-POPCOUNT: # %bb.0:
; NO-POPCOUNT-NEXT: movabsq $9223372036854775807, %rax # imm = 0x7FFFFFFFFFFFFFFF
; NO-POPCOUNT-NEXT: andq %rcx, %rax
; NO-POPCOUNT-NEXT: movq %rsi, %rcx
; NO-POPCOUNT-NEXT: shrq %rcx
; NO-POPCOUNT-NEXT: movabsq $6148914691236517205, %r8 # imm = 0x5555555555555555
; NO-POPCOUNT-NEXT: andq %r8, %rcx
; NO-POPCOUNT-NEXT: subq %rcx, %rsi
; NO-POPCOUNT-NEXT: movabsq $3689348814741910323, %r11 # imm = 0x3333333333333333
; NO-POPCOUNT-NEXT: movq %rsi, %rcx
; NO-POPCOUNT-NEXT: andq %r11, %rcx
; NO-POPCOUNT-NEXT: shrq $2, %rsi
; NO-POPCOUNT-NEXT: andq %r11, %rsi
; NO-POPCOUNT-NEXT: addq %rcx, %rsi
; NO-POPCOUNT-NEXT: movq %rsi, %rcx
; NO-POPCOUNT-NEXT: shrq $4, %rcx
; NO-POPCOUNT-NEXT: addq %rsi, %rcx
; NO-POPCOUNT-NEXT: movabsq $1085102592571150095, %r9 # imm = 0xF0F0F0F0F0F0F0F
; NO-POPCOUNT-NEXT: andq %r9, %rcx
; NO-POPCOUNT-NEXT: movabsq $72340172838076673, %r10 # imm = 0x101010101010101
; NO-POPCOUNT-NEXT: imulq %r10, %rcx
; NO-POPCOUNT-NEXT: shrq $56, %rcx
; NO-POPCOUNT-NEXT: movq %rdi, %rsi
; NO-POPCOUNT-NEXT: shrq %rsi
; NO-POPCOUNT-NEXT: andq %r8, %rsi
; NO-POPCOUNT-NEXT: subq %rsi, %rdi
; NO-POPCOUNT-NEXT: movq %rdi, %rsi
; NO-POPCOUNT-NEXT: andq %r11, %rsi
; NO-POPCOUNT-NEXT: shrq $2, %rdi
; NO-POPCOUNT-NEXT: andq %r11, %rdi
; NO-POPCOUNT-NEXT: addq %rsi, %rdi
; NO-POPCOUNT-NEXT: movq %rdi, %rsi
; NO-POPCOUNT-NEXT: shrq $4, %rsi
; NO-POPCOUNT-NEXT: addq %rdi, %rsi
; NO-POPCOUNT-NEXT: andq %r9, %rsi
; NO-POPCOUNT-NEXT: imulq %r10, %rsi
; NO-POPCOUNT-NEXT: shrq $56, %rsi
; NO-POPCOUNT-NEXT: addl %ecx, %esi
; NO-POPCOUNT-NEXT: movq %rax, %rcx
; NO-POPCOUNT-NEXT: shrq %rcx
; NO-POPCOUNT-NEXT: movabsq $1537228672809129301, %rdi # imm = 0x1555555555555555
; NO-POPCOUNT-NEXT: andq %rcx, %rdi
; NO-POPCOUNT-NEXT: subq %rdi, %rax
; NO-POPCOUNT-NEXT: movq %rax, %rcx
; NO-POPCOUNT-NEXT: andq %r11, %rcx
; NO-POPCOUNT-NEXT: shrq $2, %rax
; NO-POPCOUNT-NEXT: andq %r11, %rax
; NO-POPCOUNT-NEXT: addq %rcx, %rax
; NO-POPCOUNT-NEXT: movq %rax, %rcx
; NO-POPCOUNT-NEXT: shrq $4, %rcx
; NO-POPCOUNT-NEXT: addq %rax, %rcx
; NO-POPCOUNT-NEXT: andq %r9, %rcx
; NO-POPCOUNT-NEXT: imulq %r10, %rcx
; NO-POPCOUNT-NEXT: shrq $56, %rcx
; NO-POPCOUNT-NEXT: movq %rdx, %rax
; NO-POPCOUNT-NEXT: shrq %rax
; NO-POPCOUNT-NEXT: andq %r8, %rax
; NO-POPCOUNT-NEXT: subq %rax, %rdx
; NO-POPCOUNT-NEXT: movq %rdx, %rax
; NO-POPCOUNT-NEXT: andq %r11, %rax
; NO-POPCOUNT-NEXT: shrq $2, %rdx
; NO-POPCOUNT-NEXT: andq %r11, %rdx
; NO-POPCOUNT-NEXT: addq %rax, %rdx
; NO-POPCOUNT-NEXT: movq %rdx, %rax
; NO-POPCOUNT-NEXT: shrq $4, %rax
; NO-POPCOUNT-NEXT: addq %rdx, %rax
; NO-POPCOUNT-NEXT: andq %r9, %rax
; NO-POPCOUNT-NEXT: imulq %r10, %rax
; NO-POPCOUNT-NEXT: shrq $56, %rax
; NO-POPCOUNT-NEXT: addl %ecx, %eax
; NO-POPCOUNT-NEXT: addl %esi, %eax
; NO-POPCOUNT-NEXT: cmpb $1, %al
; NO-POPCOUNT-NEXT: sete %al
; NO-POPCOUNT-NEXT: retq
; CHECK-LABEL: ctpop_trunc_non_power2:
; CHECK: # %bb.0:
; CHECK-NEXT: pushq %rbx
; CHECK-NEXT: .cfi_def_cfa_offset 16
; CHECK-NEXT: .cfi_offset %rbx, -16
; CHECK-NEXT: movabsq $9223372036854775807, %r8 # imm = 0x7FFFFFFFFFFFFFFF
; CHECK-NEXT: movq %rcx, %r9
; CHECK-NEXT: andq %r8, %r9
; CHECK-NEXT: movq %rdi, %r11
; CHECK-NEXT: addq $-1, %r11
; CHECK-NEXT: movq %rsi, %r10
; CHECK-NEXT: adcq $-1, %r10
; CHECK-NEXT: movq %rdx, %rax
; CHECK-NEXT: adcq $-1, %rax
; CHECK-NEXT: movq %rcx, %rbx
; CHECK-NEXT: adcq %r8, %rbx
; CHECK-NEXT: andq %rdi, %r11
; CHECK-NEXT: andq %rdx, %rax
; CHECK-NEXT: orq %r11, %rax
; CHECK-NEXT: andq %rsi, %r10
; CHECK-NEXT: andq %r8, %rbx
; CHECK-NEXT: andq %rcx, %rbx
; CHECK-NEXT: orq %r10, %rbx
; CHECK-NEXT: orq %rax, %rbx
; CHECK-NEXT: sete %cl
; CHECK-NEXT: orq %rdx, %rdi
; CHECK-NEXT: orq %rsi, %r9
; CHECK-NEXT: orq %rdi, %r9
; CHECK-NEXT: setne %al
; CHECK-NEXT: andb %cl, %al
; CHECK-NEXT: popq %rbx
; CHECK-NEXT: .cfi_def_cfa_offset 8
; CHECK-NEXT: retq
%a = call i255 @llvm.ctpop.i255(i255 %x)
%b = trunc i255 %a to i8 ; largest value from ctpop is 255, fits in 8 bits.
%c = icmp eq i8 %b, 1