[PPC] Inline expansion of memcmp

This patch does an inline expansion of memcmp.
It changes the memcmp library call into an inline expansion when the size is
known at compile time and is under a target specified threshold.
This expansion is implemented in CodeGenPrepare and expands into straight line
code. The target specifies a maximum load size and the expansion works by using
this size to load the two sources, compare, and exit early if a difference is
found. It also has a special case when the memcmp result is used in a compare
to zero equality.

Differential Revision: https://reviews.llvm.org/D28637

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304313 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 121 insertions, 0 deletions

diff --git a/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll b/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
new file mode 100644
index 00000000000..3095429758f
--- /dev/null
+++ b/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
@@ -0,0 +1,121 @@
+; RUN: llc -verify-machineinstrs -mcpu=pwr8 < %s | FileCheck %s
+target datalayout = "e-m:e-i64:64-n32:64"
+target triple = "powerpc64le-unknown-linux-gnu"
+
+@zeroEqualityTest01.buffer1 = private unnamed_addr constant [3 x i32] [i32 1, i32 2, i32 4], align 4
+@zeroEqualityTest01.buffer2 = private unnamed_addr constant [3 x i32] [i32 1, i32 2, i32 3], align 4
+@zeroEqualityTest02.buffer1 = private unnamed_addr constant [4 x i32] [i32 4, i32 0, i32 0, i32 0], align 4
+@zeroEqualityTest02.buffer2 = private unnamed_addr constant [4 x i32] [i32 3, i32 0, i32 0, i32 0], align 4
+@zeroEqualityTest03.buffer1 = private unnamed_addr constant [4 x i32] [i32 0, i32 0, i32 0, i32 3], align 4
+@zeroEqualityTest03.buffer2 = private unnamed_addr constant [4 x i32] [i32 0, i32 0, i32 0, i32 4], align 4
+@zeroEqualityTest04.buffer1 = private unnamed_addr constant [15 x i32] [i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14], align 4
+@zeroEqualityTest04.buffer2 = private unnamed_addr constant [15 x i32] [i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 13], align 4
+
+; Function Attrs: nounwind readonly
+declare signext i32 @memcmp(i8* nocapture, i8* nocapture, i64) local_unnamed_addr #1
+
+; Validate with if(memcmp())
+; Function Attrs: nounwind readonly
+define signext i32 @zeroEqualityTest01() local_unnamed_addr #0 {
+entry:
+  %call = tail call signext i32 @memcmp(i8* bitcast ([3 x i32]* @zeroEqualityTest01.buffer1 to i8*), i8* bitcast ([3 x i32]* @zeroEqualityTest01.buffer2 to i8*), i64 16)
+  %not.tobool = icmp ne i32 %call, 0
+  %. = zext i1 %not.tobool to i32
+  ret i32 %.
+
+  ; CHECK-LABEL: @zeroEqualityTest01
+  ; CHECK-LABEL: %res_block
+  ; CHECK: li 3, 1
+  ; CHECK-NEXT: clrldi
+  ; CHECK-NEXT: blr
+  ; CHECK: li 3, 0
+  ; CHECK-NEXT: clrldi
+  ; CHECK-NEXT: blr
+}
+
+; Validate with if(memcmp() == 0)
+; Function Attrs: nounwind readonly
+define signext i32 @zeroEqualityTest02() local_unnamed_addr #0 {
+entry:
+  %call = tail call signext i32 @memcmp(i8* bitcast ([4 x i32]* @zeroEqualityTest02.buffer1 to i8*), i8* bitcast ([4 x i32]* @zeroEqualityTest02.buffer2 to i8*), i64 16)
+  %not.cmp = icmp ne i32 %call, 0
+  %. = zext i1 %not.cmp to i32
+  ret i32 %.
+
+  ; CHECK-LABEL: @zeroEqualityTest02
+  ; CHECK-LABEL: %res_block
+  ; CHECK: li 3, 1
+  ; CHECK-NEXT: clrldi
+  ; CHECK-NEXT: blr
+  ; CHECK: li 3, 0
+  ; CHECK-NEXT: clrldi
+  ; CHECK-NEXT: blr
+}
+
+; Validate with > 0
+; Function Attrs: nounwind readonly
+define signext i32 @zeroEqualityTest03() local_unnamed_addr #0 {
+entry:
+  %call = tail call signext i32 @memcmp(i8* bitcast ([4 x i32]* @zeroEqualityTest02.buffer1 to i8*), i8* bitcast ([4 x i32]* @zeroEqualityTest02.buffer2 to i8*), i64 16)
+  %not.cmp = icmp slt i32 %call, 1
+  %. = zext i1 %not.cmp to i32
+  ret i32 %.
+
+  ; CHECK-LABEL: @zeroEqualityTest03
+  ; CHECK-LABEL: %res_block
+  ; CHECK: cmpld
+  ; CHECK-NEXT: li [[LI:[0-9]+]], 1
+  ; CHECK-NEXT: li [[LI2:[0-9]+]], -1
+  ; CHECK-NEXT: isel [[ISEL:[0-9]+]], [[LI2]], [[LI]], 0
+}
+
+; Validate with < 0
+; Function Attrs: nounwind readonly
+define signext i32 @zeroEqualityTest04() local_unnamed_addr #0 {
+entry:
+  %call = tail call signext i32 @memcmp(i8* bitcast ([4 x i32]* @zeroEqualityTest03.buffer1 to i8*), i8* bitcast ([4 x i32]* @zeroEqualityTest03.buffer2 to i8*), i64 16)
+  %call.lobit = lshr i32 %call, 31
+  %call.lobit.not = xor i32 %call.lobit, 1
+  ret i32 %call.lobit.not
+
+  ; CHECK-LABEL: @zeroEqualityTest04
+  ; CHECK-LABEL: %res_block
+  ; CHECK: cmpld
+  ; CHECK-NEXT: li [[LI:[0-9]+]], 1
+  ; CHECK-NEXT: li [[LI2:[0-9]+]], -1
+  ; CHECK-NEXT: isel [[ISEL:[0-9]+]], [[LI2]], [[LI]], 0
+}
+
+; Validate with memcmp()?:
+; Function Attrs: nounwind readonly
+define signext i32 @zeroEqualityTest05() local_unnamed_addr #0 {
+entry:
+  %call = tail call signext i32 @memcmp(i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer1 to i8*), i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer2 to i8*), i64 16)
+  %not.tobool = icmp eq i32 %call, 0
+  %cond = zext i1 %not.tobool to i32
+  ret i32 %cond
+
+  ; CHECK-LABEL: @zeroEqualityTest05
+  ; CHECK-LABEL: %res_block
+  ; CHECK: li 3, 1
+  ; CHECK: li 3, 0
+}
+
+; Validate with !memcmp()?:
+; Function Attrs: nounwind readonly
+define signext i32 @zeroEqualityTest06() local_unnamed_addr #0 {
+entry:
+  %call = tail call signext i32 @memcmp(i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer1 to i8*), i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer2 to i8*), i64 16)
+  %not.lnot = icmp ne i32 %call, 0
+  %cond = zext i1 %not.lnot to i32
+  ret i32 %cond
+
+  ; CHECK-LABEL: @zeroEqualityTest06
+  ; CHECK-LABEL: %res_block
+  ; CHECK: li 3, 1
+  ; CHECK-NEXT: clrldi
+  ; CHECK-NEXT: blr
+  ; CHECK: li 3, 0
+  ; CHECK-NEXT: clrldi
+  ; CHECK-NEXT: blr
+}