From 8e770608715067248f27b0cbb8726d2cf4f69817 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Wed, 14 Oct 2015 21:47:03 +0000
Subject: [PATCH] add x86 codegen tests for 'add nsw' followed by 'sext'

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@250332 91177308-0d34-0410-b5e6-96231b3b80d8
---
 test/CodeGen/X86/add-nsw-sext.ll | 179 +++++++++++++++++++++++++++++++
 1 file changed, 179 insertions(+)
 create mode 100644 test/CodeGen/X86/add-nsw-sext.ll

diff --git a/test/CodeGen/X86/add-nsw-sext.ll b/test/CodeGen/X86/add-nsw-sext.ll
new file mode 100644
index 00000000000..1c2558d60e2
--- /dev/null
+++ b/test/CodeGen/X86/add-nsw-sext.ll
@@ -0,0 +1,179 @@
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s
+
+; The fundamental problem: an add separated from other arithmetic by a sext can't
+; be combined with the later instructions. However, if the first add is 'nsw', 
+; then we can promote the sext 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:    leaq (%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 i8* @gep8(i32 %i, i8* %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, i8* %x, i64 %ext
+  ret i8* %idx
+}
+
+define i16* @gep16(i32 %i, i16* %x) {
+; CHECK-LABEL: gep16:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    addl $-5, %edi
+; CHECK-NEXT:    movslq %edi, %rax
+; CHECK-NEXT:    leaq (%rsi,%rax,2), %rax
+; CHECK-NEXT:    retq
+
+  %add = add nsw i32 %i, -5
+  %ext = sext i32 %add to i64
+  %idx = getelementptr i16, i16* %x, i64 %ext
+  ret i16* %idx
+}
+
+define i32* @gep32(i32 %i, i32* %x) {
+; CHECK-LABEL: gep32:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    addl $5, %edi
+; CHECK-NEXT:    movslq %edi, %rax
+; CHECK-NEXT:    leaq (%rsi,%rax,4), %rax
+; CHECK-NEXT:    retq
+
+  %add = add nsw i32 %i, 5
+  %ext = sext i32 %add to i64
+  %idx = getelementptr i32, i32* %x, i64 %ext
+  ret i32* %idx
+}
+
+define i64* @gep64(i32 %i, i64* %x) {
+; CHECK-LABEL: gep64:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    addl $-5, %edi
+; CHECK-NEXT:    movslq %edi, %rax
+; CHECK-NEXT:    leaq (%rsi,%rax,8), %rax
+; CHECK-NEXT:    retq
+
+  %add = add nsw i32 %i, -5
+  %ext = sext i32 %add to i64
+  %idx = getelementptr i64, i64* %x, i64 %ext
+  ret i64* %idx
+}
+
+; LEA can't scale by 16, but the adds can still be combined into an LEA.
+
+define i128* @gep128(i32 %i, i128* %x) {
+; CHECK-LABEL: gep128:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    addl $5, %edi
+; CHECK-NEXT:    movslq %edi, %rax
+; CHECK-NEXT:    shlq $4, %rax
+; CHECK-NEXT:    addq %rsi, %rax
+; CHECK-NEXT:    retq
+
+  %add = add nsw i32 %i, 5
+  %ext = sext i32 %add to i64
+  %idx = getelementptr i128, i128* %x, i64 %ext
+  ret i128* %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(i32* %a, i32 %i) {
+; CHECK-LABEL: PR20134:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    leal 1(%rsi), %eax
+; CHECK-NEXT:    cltq
+; CHECK-NEXT:    movl (%rdi,%rax,4), %eax
+; CHECK-NEXT:    leal 2(%rsi), %ecx
+; CHECK-NEXT:    movslq %ecx, %rcx
+; CHECK-NEXT:    addl (%rdi,%rcx,4), %eax
+; CHECK-NEXT:    movslq %esi, %rcx
+; CHECK-NEXT:    movl %eax, (%rdi,%rcx,4)
+; CHECK-NEXT:    retq
+
+  %add1 = add nsw i32 %i, 1
+  %idx1 = sext i32 %add1 to i64
+  %gep1 = getelementptr i32, i32* %a, i64 %idx1
+  %load1 = load i32, i32* %gep1, align 4
+
+  %add2 = add nsw i32 %i, 2
+  %idx2 = sext i32 %add2 to i64
+  %gep2 = getelementptr i32, i32* %a, i64 %idx2
+  %load2 = load i32, i32* %gep2, align 4
+
+  %add3 = add i32 %load1, %load2
+  %idx3 = sext i32 %i to i64
+  %gep3 = getelementptr i32, i32* %a, i64 %idx3
+  store i32 %add3, i32* %gep3, align 4
+  ret void
+}
+
-- 
2.34.1