[PowerPC] Use subfic instruction for subtract from immediate

Provide a 64-bit pattern to use SUBFIC for subtracting from a 16-bit immediate.
The corresponding pattern already exists for 32-bit integers.

Committing on behalf of Hiroshi Inoue.

Differential Revision: https://reviews.llvm.org/D29387


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296144 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 41 insertions, 0 deletions

diff --git a/test/CodeGen/PowerPC/subtract_from_imm.ll b/test/CodeGen/PowerPC/subtract_from_imm.ll
new file mode 100644
index 00000000000..8fa07b671a3
--- /dev/null
+++ b/test/CodeGen/PowerPC/subtract_from_imm.ll
@@ -0,0 +1,41 @@
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu < %s | FileCheck %s
+
+; Make sure that the subfic is generated iff possible
+
+define i64 @subtract_from_imm1(i64 %v) nounwind readnone {
+entry:
+; CHECK-LABEL: subtract_from_imm1
+; CHECK: subfic 3, 3, 32767
+; CHECK: blr
+  %sub = sub i64 32767, %v
+  ret i64 %sub
+}
+
+define i64 @subtract_from_imm2(i64 %v) nounwind readnone {
+entry:
+; CHECK-LABEL: subtract_from_imm2
+; CHECK-NOT: subfic
+; CHECK: blr
+  %sub = sub i64 32768, %v
+  ret i64 %sub
+}
+
+define i64 @subtract_from_imm3(i64 %v) nounwind readnone {
+entry:
+; CHECK-LABEL: subtract_from_imm3
+; CHECK: subfic 3, 3, -32768
+; CHECK: blr
+  %sub = sub i64 -32768, %v
+  ret i64 %sub
+}
+
+define i64 @subtract_from_imm4(i64 %v) nounwind readnone {
+entry:
+; CHECK-LABEL: subtract_from_imm4
+; CHECK-NOT: subfic
+; CHECK: blr
+  %sub = sub i64 -32769, %v
+  ret i64 %sub
+}
+