llvm/test/CodeGen/X86/GlobalISel/add-ext.ll

; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=x86_64-unknown-unknown -global-isel | 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:    addl $5, %edi
; CHECK-NEXT:    movslq %edi, %rax
; CHECK-NEXT:    addq $7, %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:    addl $5, %edi
; CHECK-NEXT:    movslq %edi, %rax
; CHECK-NEXT:    addq %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:    addl $-5, %edi
; CHECK-NEXT:    movslq %edi, %rax
; CHECK-NEXT:    shlq $3, %rax
; CHECK-NEXT:    addq %rsi, %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:    addl $5, %edi
; CHECK-NEXT:    movslq %edi, %rax
; CHECK-NEXT:    addq %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:    addl $-5, %edi
; CHECK-NEXT:    movslq %edi, %rax
; CHECK-NEXT:    imulq $2, %rax, %rax
; CHECK-NEXT:    addq %rsi, %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:    addl $5, %edi
; CHECK-NEXT:    movslq %edi, %rax
; CHECK-NEXT:    imulq $4, %rax, %rax
; CHECK-NEXT:    addq %rsi, %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:    addl $-5, %edi
; CHECK-NEXT:    movslq %edi, %rax
; CHECK-NEXT:    imulq $8, %rax, %rax
; CHECK-NEXT:    addq %rsi, %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:    addl $5, %edi
; CHECK-NEXT:    movslq %edi, %rax
; CHECK-NEXT:    imulq $16, %rax, %rax
; CHECK-NEXT:    addq %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:    # kill: def $esi killed $esi def $rsi
; CHECK-NEXT:    leal 1(%rsi), %eax
; CHECK-NEXT:    cltq
; CHECK-NEXT:    imulq $4, %rax, %rax
; CHECK-NEXT:    addq %rdi, %rax
; CHECK-NEXT:    leal 2(%rsi), %ecx
; CHECK-NEXT:    movslq %ecx, %rcx
; CHECK-NEXT:    imulq $4, %rcx, %rcx
; CHECK-NEXT:    addq %rdi, %rcx
; CHECK-NEXT:    movl (%rcx), %ecx
; CHECK-NEXT:    addl (%rax), %ecx
; CHECK-NEXT:    movslq %esi, %rax
; CHECK-NEXT:    imulq $4, %rax, %rax
; CHECK-NEXT:    addq %rdi, %rax
; CHECK-NEXT:    movl %ecx, (%rax)
; 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:    # kill: def $esi killed $esi def $rsi
; CHECK-NEXT:    leal 1(%rsi), %eax
; CHECK-NEXT:    movl %eax, %eax
; CHECK-NEXT:    imulq $4, %rax, %rax
; CHECK-NEXT:    addq %rdi, %rax
; CHECK-NEXT:    leal 2(%rsi), %ecx
; CHECK-NEXT:    movl %ecx, %ecx
; CHECK-NEXT:    imulq $4, %rcx, %rcx
; CHECK-NEXT:    addq %rdi, %rcx
; CHECK-NEXT:    movl (%rcx), %ecx
; CHECK-NEXT:    addl (%rax), %ecx
; CHECK-NEXT:    movl %esi, %eax
; CHECK-NEXT:    imulq $4, %rax, %rax
; CHECK-NEXT:    addq %rdi, %rax
; CHECK-NEXT:    movl %ecx, (%rax)
; 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
}