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llvm-mirror/test/CodeGen/X86/pr33290.ll
Sanjay Patel 6fae7ed86a [DAGCombiner] allow narrowing of add followed by truncate
trunc (add X, C ) --> add (trunc X), C'

If we're throwing away the top bits of an 'add' instruction, do it in the narrow destination type.
This makes the truncate-able opcode list identical to the sibling transform done in IR (in instcombine).

This change used to show regressions for x86, but those are gone after D55494. 
This gets us closer to deleting the x86 custom function (combineTruncatedArithmetic) 
that does almost the same thing.

Differential Revision: https://reviews.llvm.org/D55866

llvm-svn: 350006
2018-12-22 17:10:31 +00:00

52 lines
1.6 KiB
LLVM

; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=i686-unknown-unknown | FileCheck %s --check-prefix=X86
; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s --check-prefix=X64
@a = common global i32 0, align 4
@c = common local_unnamed_addr global i8 0, align 1
@b = common local_unnamed_addr global i32* null, align 8
define void @e() {
; X86-LABEL: e:
; X86: # %bb.0: # %entry
; X86-NEXT: movl b, %eax
; X86-NEXT: .p2align 4, 0x90
; X86-NEXT: .LBB0_1: # %for.cond
; X86-NEXT: # =>This Inner Loop Header: Depth=1
; X86-NEXT: movzbl c, %ecx
; X86-NEXT: movb $0, c
; X86-NEXT: leal a+2(%ecx), %ecx
; X86-NEXT: movl %ecx, (%eax)
; X86-NEXT: jmp .LBB0_1
;
; X64-LABEL: e:
; X64: # %bb.0: # %entry
; X64-NEXT: movq {{.*}}(%rip), %rax
; X64-NEXT: movl $a, %esi
; X64-NEXT: .p2align 4, 0x90
; X64-NEXT: .LBB0_1: # %for.cond
; X64-NEXT: # =>This Inner Loop Header: Depth=1
; X64-NEXT: movzbl {{.*}}(%rip), %edx
; X64-NEXT: addq %rsi, %rdx
; X64-NEXT: setb %cl
; X64-NEXT: addq $2, %rdx
; X64-NEXT: adcb $0, %cl
; X64-NEXT: movb %cl, {{.*}}(%rip)
; X64-NEXT: movl %edx, (%rax)
; X64-NEXT: jmp .LBB0_1
entry:
%0 = load i32*, i32** @b, align 8
br label %for.cond
for.cond:
%1 = load i8, i8* @c, align 1
%conv = zext i8 %1 to i128
%add = add nuw nsw i128 %conv, add (i128 ptrtoint (i32* @a to i128), i128 2)
%2 = lshr i128 %add, 64
%conv1 = trunc i128 %2 to i8
store i8 %conv1, i8* @c, align 1
%conv2 = trunc i128 %add to i32
store i32 %conv2, i32* %0, align 4
br label %for.cond
}