; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s
; The fundamental problem: an add separated from other arithmetic by a sign or
; zero extension can't be combined with the later instructions. However, if the
; first add is 'nsw' or 'nuw' respectively, then we can promote the extension
; ahead of that add to allow optimizations.
define i64 @add_nsw_consts(i32 %i) {
; CHECK-LABEL: add_nsw_consts:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: addq $12, %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, 5
%ext = sext i32 %add to i64
%idx = add i64 %ext, 7
ret i64 %idx
}
; An x86 bonus: If we promote the sext ahead of the 'add nsw',
; we allow LEA formation and eliminate an add instruction.
define i64 @add_nsw_sext_add(i32 %i, i64 %x) {
; CHECK-LABEL: add_nsw_sext_add:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: leaq 5(%rax,%rsi), %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, 5
%ext = sext i32 %add to i64
%idx = add i64 %x, %ext
ret i64 %idx
}
; Throw in a scale (left shift) because an LEA can do that too.
; Use a negative constant (LEA displacement) to verify that's handled correctly.
define i64 @add_nsw_sext_lsh_add(i32 %i, i64 %x) {
; CHECK-LABEL: add_nsw_sext_lsh_add:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: leaq -40(%rsi,%rax,8), %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, -5
%ext = sext i32 %add to i64
%shl = shl i64 %ext, 3
%idx = add i64 %x, %shl
ret i64 %idx
}
; Don't promote the sext if it has no users. The wider add instruction needs an
; extra byte to encode.
define i64 @add_nsw_sext(i32 %i, i64 %x) {
; CHECK-LABEL: add_nsw_sext:
; CHECK: # %bb.0:
; CHECK-NEXT: addl $5, %edi
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, 5
%ext = sext i32 %add to i64
ret i64 %ext
}
; The typical use case: a 64-bit system where an 'int' is used as an index into an array.
define ptr @gep8(i32 %i, ptr %x) {
; CHECK-LABEL: gep8:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: leaq 5(%rax,%rsi), %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, 5
%ext = sext i32 %add to i64
%idx = getelementptr i8, ptr %x, i64 %ext
ret ptr %idx
}
define ptr @gep16(i32 %i, ptr %x) {
; CHECK-LABEL: gep16:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: leaq -10(%rsi,%rax,2), %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, -5
%ext = sext i32 %add to i64
%idx = getelementptr i16, ptr %x, i64 %ext
ret ptr %idx
}
define ptr @gep32(i32 %i, ptr %x) {
; CHECK-LABEL: gep32:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: leaq 20(%rsi,%rax,4), %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, 5
%ext = sext i32 %add to i64
%idx = getelementptr i32, ptr %x, i64 %ext
ret ptr %idx
}
define ptr @gep64(i32 %i, ptr %x) {
; CHECK-LABEL: gep64:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: leaq -40(%rsi,%rax,8), %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, -5
%ext = sext i32 %add to i64
%idx = getelementptr i64, ptr %x, i64 %ext
ret ptr %idx
}
; LEA can't scale by 16, but the adds can still be combined into an LEA.
define ptr @gep128(i32 %i, ptr %x) {
; CHECK-LABEL: gep128:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %edi, %rax
; CHECK-NEXT: shlq $4, %rax
; CHECK-NEXT: leaq 80(%rax,%rsi), %rax
; CHECK-NEXT: retq
%add = add nsw i32 %i, 5
%ext = sext i32 %add to i64
%idx = getelementptr i128, ptr %x, i64 %ext
ret ptr %idx
}
; A bigger win can be achieved when there is more than one use of the
; sign extended value. In this case, we can eliminate sign extension
; instructions plus use more efficient addressing modes for memory ops.
define void @PR20134(ptr %a, i32 %i) {
; CHECK-LABEL: PR20134:
; CHECK: # %bb.0:
; CHECK-NEXT: movslq %esi, %rax
; CHECK-NEXT: movl 4(%rdi,%rax,4), %ecx
; CHECK-NEXT: addl 8(%rdi,%rax,4), %ecx
; CHECK-NEXT: movl %ecx, (%rdi,%rax,4)
; CHECK-NEXT: retq
%add1 = add nsw i32 %i, 1
%idx1 = sext i32 %add1 to i64
%gep1 = getelementptr i32, ptr %a, i64 %idx1
%load1 = load i32, ptr %gep1, align 4
%add2 = add nsw i32 %i, 2
%idx2 = sext i32 %add2 to i64
%gep2 = getelementptr i32, ptr %a, i64 %idx2
%load2 = load i32, ptr %gep2, align 4
%add3 = add i32 %load1, %load2
%idx3 = sext i32 %i to i64
%gep3 = getelementptr i32, ptr %a, i64 %idx3
store i32 %add3, ptr %gep3, align 4
ret void
}
; The same as @PR20134 but sign extension is replaced with zero extension
define void @PR20134_zext(ptr %a, i32 %i) {
; CHECK-LABEL: PR20134_zext:
; CHECK: # %bb.0:
; CHECK-NEXT: movl %esi, %eax
; CHECK-NEXT: movl 4(%rdi,%rax,4), %ecx
; CHECK-NEXT: addl 8(%rdi,%rax,4), %ecx
; CHECK-NEXT: movl %ecx, (%rdi,%rax,4)
; CHECK-NEXT: retq
%add1 = add nuw i32 %i, 1
%idx1 = zext i32 %add1 to i64
%gep1 = getelementptr i32, ptr %a, i64 %idx1
%load1 = load i32, ptr %gep1, align 4
%add2 = add nuw i32 %i, 2
%idx2 = zext i32 %add2 to i64
%gep2 = getelementptr i32, ptr %a, i64 %idx2
%load2 = load i32, ptr %gep2, align 4
%add3 = add i32 %load1, %load2
%idx3 = zext i32 %i to i64
%gep3 = getelementptr i32, ptr %a, i64 %idx3
store i32 %add3, ptr %gep3, align 4
ret void
}
Codebase Browser
llvm