[PowerPC] add XLC compat builtin __abs

[shchenz]

Summary

This is supplement of D104386, we add one more XLC compat builtin __abs.

[shchenz]

gentle ping

[jsji]

LGTM. Thanks.

clang/lib/Basic/Targets/PPC.cpp

static void defineXLCompatMacros(MacroBuilder &Builder) {
   Builder.defineMacro("__cnttz4", "__builtin_ctz");
   Builder.defineMacro("__cnttz8", "__builtin_ctzll");
   Builder.defineMacro("__darn", "__builtin_darn");
   Builder.defineMacro("__darn_32", "__builtin_darn_32");
   Builder.defineMacro("__darn_raw", "__builtin_darn_raw");
   Builder.defineMacro("__dcbf", "__builtin_dcbf");
   Builder.defineMacro("__fmadd", "__builtin_fma");
   Builder.defineMacro("__fmadds", "__builtin_fmaf");
+  Builder.defineMacro("__abs", "__builtin_abs");
   Builder.defineMacro("__labs", "__builtin_labs");
   Builder.defineMacro("__llabs", "__builtin_llabs");
   Builder.defineMacro("__popcnt4", "__builtin_popcount");
   Builder.defineMacro("__popcnt8", "__builtin_popcountll");
   Builder.defineMacro("__readflm", "__builtin_readflm");
   Builder.defineMacro("__rotatel4", "__builtin_rotateleft32");
   Builder.defineMacro("__rotatel8", "__builtin_rotateleft64");
   Builder.defineMacro("__rdlam", "__builtin_ppc_rdlam");

clang/test/CodeGen/PowerPC/builtins-ppc-xlcompat-macros.c

 // REQUIRES: powerpc-registered-target
 // RUN: %clang_cc1 -no-opaque-pointers -triple powerpc64-unknown-linux-gnu \
 // RUN:   -emit-llvm %s -o - -target-cpu pwr7 | FileCheck %s --check-prefixes=64BIT --check-prefix=BOTH
 // RUN: %clang_cc1 -no-opaque-pointers -triple powerpc64le-unknown-linux-gnu \
 // RUN:   -emit-llvm %s -o - -target-cpu pwr8 | FileCheck %s --check-prefixes=64BIT --check-prefix=BOTH
 // RUN: %clang_cc1 -no-opaque-pointers -triple powerpc-unknown-aix \
 // RUN:   -emit-llvm %s -o - -target-cpu pwr7 | FileCheck %s --check-prefixes=32BIT --check-prefix=BOTH
 // RUN: %clang_cc1 -no-opaque-pointers -triple powerpc64-unknown-aix \
 // RUN:   -emit-llvm %s -o - -target-cpu pwr7 | FileCheck %s --check-prefixes=64BIT --check-prefix=BOTH
 
 // Will not be adding include files to avoid any dependencies on the system.
 // Required for size_t. Usually found in stddef.h.
 typedef __SIZE_TYPE__ size_t;
 
+// BOTH-LABEL: @testabs(
+// BOTH-NEXT:  entry:
+// BOTH-NEXT:    [[A_ADDR:%.*]] = alloca i32, align 4
+// BOTH-NEXT:    store i32 [[A:%.*]], i32* [[A_ADDR]], align 4
+// BOTH-NEXT:    [[TMP0:%.*]] = load i32, i32* [[A_ADDR]], align 4
+// BOTH-NEXT:    [[NEG:%.*]] = sub nsw i32 0, [[TMP0]]
+// BOTH-NEXT:    [[ABSCOND:%.*]] = icmp slt i32 [[TMP0]], 0
+// BOTH-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i32 [[NEG]], i32 [[TMP0]]
+// BOTH-NEXT:    ret i32 [[ABS]]
+signed int testabs(signed int a) {
+  return __abs(a);
+}
+
 // 64BIT-LABEL: @testlabs(
 // 64BIT-NEXT:  entry:
 // 64BIT-NEXT:    [[A_ADDR:%.*]] = alloca i64, align 8
 // 64BIT-NEXT:    store i64 [[A:%.*]], i64* [[A_ADDR]], align 8
 // 64BIT-NEXT:    [[TMP0:%.*]] = load i64, i64* [[A_ADDR]], align 8
 // 64BIT-NEXT:    [[NEG:%.*]] = sub nsw i64 0, [[TMP0]]
 // 64BIT-NEXT:    [[ABSCOND:%.*]] = icmp slt i64 [[TMP0]], 0
 // 64BIT-NEXT:    [[ABS:%.*]] = select i1 [[ABSCOND]], i64 [[NEG]], i64 [[TMP0]]