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llvm-mirror/test/CodeGen/X86/divide-by-constant.ll

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Add a couple dag combines to transform mulhi/mullo into a wider multiply when the wider type is legal. This allows us to compile: define zeroext i16 @test1(i16 zeroext %x) nounwind { entry: %div = udiv i16 %x, 33 ret i16 %div } into: test1: # @test1 movzwl 4(%esp), %eax imull $63551, %eax, %eax # imm = 0xF83F shrl $21, %eax ret instead of: test1: # @test1 movw $-1985, %ax # imm = 0xFFFFFFFFFFFFF83F mulw 4(%esp) andl $65504, %edx # imm = 0xFFE0 movl %edx, %eax shrl $5, %eax ret Implementing rdar://8760399 and example #4 from: http://blog.regehr.org/archives/320 We should implement the same thing for [su]mul_hilo, but I don't have immediate plans to do this. llvm-svn: 121696
2010-12-13 09:39:01 +01:00
; RUN: llc < %s -mtriple=i686-pc-linux-gnu -asm-verbose=0 | FileCheck %s
Fix for PR2164: allow transforming arbitrary-width unsigned divides into multiplies. Some more cleverness would be nice, though. It would be nice if we could do this transformation on illegal types. Also, we would prefer a narrower constant when possible so that we can use a narrower multiply, which can be cheaper. llvm-svn: 60283
2008-11-30 07:02:26 +01:00
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
target triple = "i686-pc-linux-gnu"
Add a couple dag combines to transform mulhi/mullo into a wider multiply when the wider type is legal. This allows us to compile: define zeroext i16 @test1(i16 zeroext %x) nounwind { entry: %div = udiv i16 %x, 33 ret i16 %div } into: test1: # @test1 movzwl 4(%esp), %eax imull $63551, %eax, %eax # imm = 0xF83F shrl $21, %eax ret instead of: test1: # @test1 movw $-1985, %ax # imm = 0xFFFFFFFFFFFFF83F mulw 4(%esp) andl $65504, %edx # imm = 0xFFE0 movl %edx, %eax shrl $5, %eax ret Implementing rdar://8760399 and example #4 from: http://blog.regehr.org/archives/320 We should implement the same thing for [su]mul_hilo, but I don't have immediate plans to do this. llvm-svn: 121696
2010-12-13 09:39:01 +01:00
define zeroext i16 @test1(i16 zeroext %x) nounwind {
Fix for PR2164: allow transforming arbitrary-width unsigned divides into multiplies. Some more cleverness would be nice, though. It would be nice if we could do this transformation on illegal types. Also, we would prefer a narrower constant when possible so that we can use a narrower multiply, which can be cheaper. llvm-svn: 60283
2008-11-30 07:02:26 +01:00
entry:
Add a couple dag combines to transform mulhi/mullo into a wider multiply when the wider type is legal. This allows us to compile: define zeroext i16 @test1(i16 zeroext %x) nounwind { entry: %div = udiv i16 %x, 33 ret i16 %div } into: test1: # @test1 movzwl 4(%esp), %eax imull $63551, %eax, %eax # imm = 0xF83F shrl $21, %eax ret instead of: test1: # @test1 movw $-1985, %ax # imm = 0xFFFFFFFFFFFFF83F mulw 4(%esp) andl $65504, %edx # imm = 0xFFE0 movl %edx, %eax shrl $5, %eax ret Implementing rdar://8760399 and example #4 from: http://blog.regehr.org/archives/320 We should implement the same thing for [su]mul_hilo, but I don't have immediate plans to do this. llvm-svn: 121696
2010-12-13 09:39:01 +01:00
%div = udiv i16 %x, 33
ret i16 %div
; CHECK: test1:
; CHECK: imull $63551, %eax, %eax
; CHECK-NEXT: shrl $21, %eax
; CHECK-NEXT: ret
}
define zeroext i16 @test2(i8 signext %x, i16 zeroext %c) nounwind readnone ssp noredzone {
entry:
%div = udiv i16 %c, 3
ret i16 %div
; CHECK: test2:
; CHECK: imull $43691, %eax, %eax
; CHECK-NEXT: shrl $17, %eax
; CHECK-NEXT: ret
}
define zeroext i8 @test3(i8 zeroext %x, i8 zeroext %c) nounwind readnone ssp noredzone {
entry:
%div = udiv i8 %c, 3
ret i8 %div
; CHECK: test3:
Reapply 122353-122355 with fixes. 122354 was wrong; the shift type was needed one place, the shift count type another. The transform in 123555 had the same problem. llvm-svn: 122366
2010-12-21 22:55:50 +01:00
; CHECK: movzbl 8(%esp), %eax
; CHECK-NEXT: imull $171, %eax, %eax
; CHECK-NEXT: shrl $9, %eax
Add a couple dag combines to transform mulhi/mullo into a wider multiply when the wider type is legal. This allows us to compile: define zeroext i16 @test1(i16 zeroext %x) nounwind { entry: %div = udiv i16 %x, 33 ret i16 %div } into: test1: # @test1 movzwl 4(%esp), %eax imull $63551, %eax, %eax # imm = 0xF83F shrl $21, %eax ret instead of: test1: # @test1 movw $-1985, %ax # imm = 0xFFFFFFFFFFFFF83F mulw 4(%esp) andl $65504, %edx # imm = 0xFFE0 movl %edx, %eax shrl $5, %eax ret Implementing rdar://8760399 and example #4 from: http://blog.regehr.org/archives/320 We should implement the same thing for [su]mul_hilo, but I don't have immediate plans to do this. llvm-svn: 121696
2010-12-13 09:39:01 +01:00
; CHECK-NEXT: ret
}
define signext i16 @test4(i16 signext %x) nounwind {
entry:
%div = sdiv i16 %x, 33 ; <i32> [#uses=1]
Fix for PR2164: allow transforming arbitrary-width unsigned divides into multiplies. Some more cleverness would be nice, though. It would be nice if we could do this transformation on illegal types. Also, we would prefer a narrower constant when possible so that we can use a narrower multiply, which can be cheaper. llvm-svn: 60283
2008-11-30 07:02:26 +01:00
ret i16 %div
merge two tests llvm-svn: 121847
2010-12-15 06:58:59 +01:00
; CHECK: test4:
The signed version of our "magic number" computation for the integer approximation of a constant had a minor typo introduced when copying it from the book, which caused it to favor negative approximations over positive approximations in many cases. Positive approximations require fewer operations beyond the multiplication. In the case of division by 3, we still generate code that is a single instruction larger than GCC's code. llvm-svn: 126097
2011-02-21 01:22:02 +01:00
; CHECK: imull $1986, %eax, %eax
Fix for PR2164: allow transforming arbitrary-width unsigned divides into multiplies. Some more cleverness would be nice, though. It would be nice if we could do this transformation on illegal types. Also, we would prefer a narrower constant when possible so that we can use a narrower multiply, which can be cheaper. llvm-svn: 60283
2008-11-30 07:02:26 +01:00
}
merge two tests llvm-svn: 121847
2010-12-15 06:58:59 +01:00
define i32 @test5(i32 %A) nounwind {
%tmp1 = udiv i32 %A, 1577682821 ; <i32> [#uses=1]
ret i32 %tmp1
; CHECK: test5:
; CHECK: movl $365384439, %eax
; CHECK: mull 4(%esp)
}
Teach DAGCombine to fold fold (sra (trunc (sr x, c1)), c2) -> (trunc (sra x, c1+c2) when c1 equals the amount of bits that are truncated off. This happens all the time when a smul is promoted to a larger type. On x86-64 we now compile "int test(int x) { return x/10; }" into movslq %edi, %rax imulq $1717986919, %rax, %rax movq %rax, %rcx shrq $63, %rcx sarq $34, %rax <- used to be "shrq $32, %rax; sarl $2, %eax" addl %ecx, %eax This fires 96 times in gcc.c on x86-64. llvm-svn: 124559
2011-01-30 17:38:43 +01:00
define signext i16 @test6(i16 signext %x) nounwind {
entry:
%div = sdiv i16 %x, 10
ret i16 %div
; CHECK: test6:
; CHECK: imull $26215, %eax, %eax
; CHECK: shrl $31, %ecx
; CHECK: sarl $18, %eax
}
BuildUDIV: If the divisor is even we can simplify the fixup of the multiplied value by introducing an early shift. This allows us to compile "unsigned foo(unsigned x) { return x/28; }" into shrl $2, %edi imulq $613566757, %rdi, %rax shrq $32, %rax ret instead of movl %edi, %eax imulq $613566757, %rax, %rcx shrq $32, %rcx subl %ecx, %eax shrl %eax addl %ecx, %eax shrl $4, %eax on x86_64 llvm-svn: 127829
2011-03-17 21:39:14 +01:00
define i32 @test7(i32 %x) nounwind {
%div = udiv i32 %x, 28
ret i32 %div
; CHECK: test7:
; CHECK: shrl $2
; CHECK: movl $613566757
; CHECK: mull
; CHECK-NOT: shrl
; CHECK: ret
}
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