[PATCH] D22011: [SystemZ] Generate fewer instructions for (sub <constant>, x)

[Assem Bsoul via llvm-commits]

assem updated the summary for this revision.
assem updated this revision to Diff 63711.
assem added a comment.

I have updated the patch based on Ulrich's comments, i.e., sgrk is used now. I have also updated the summary of the patch.


http://reviews.llvm.org/D22011

Files:
  lib/Target/SystemZ/SystemZInstrInfo.td
  test/CodeGen/SystemZ/int-sub-10.ll

Index: test/CodeGen/SystemZ/int-sub-10.ll
===================================================================
--- /dev/null
+++ test/CodeGen/SystemZ/int-sub-10.ll
@@ -0,0 +1,22 @@
+; Test of subtraction that involves a constant as the first operand
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z196 | FileCheck %s
+
+; Check highest 16-bit signed int immediate value.
+define i64 @f1(i64 %a) {
+; CHECK-LABEL: f1:
+; CHECK: lghi %r0, 32767
+; CHECK: sgrk %r2, %r0, %r2
+; CHECK: br %r14
+  %sub = sub i64 32767, %a
+  ret i64 %sub
+}
+; Check highest 32-bit signed int immediate value.
+define i64 @f2(i64 %a) {
+; CHECK-LABEL: f2:
+; CHECK: lgfi %r0, 2147483647
+; CHECK: sgrk %r2, %r0, %r2
+; CHECK: br %r14
+  %sub = sub i64 2147483647, %a
+  ret i64 %sub
+}
Index: lib/Target/SystemZ/SystemZInstrInfo.td
===================================================================
--- lib/Target/SystemZ/SystemZInstrInfo.td
+++ lib/Target/SystemZ/SystemZInstrInfo.td
@@ -1685,6 +1685,14 @@
 def : Pat<(and (xor GR64:$x, (i64 -1)), GR64:$y),
                           (XGR GR64:$y, (NGR GR64:$y, GR64:$x))>;

+// Generate fewer instructions for (sub <constant>, x) if the constant can fit
+// in immediate field.
+def : Pat<(sub imm64sx16:$imm, GR64:$x),
+                     (SGRK (LGHI imm64sx16:$imm), GR64:$x)>;
+
+def : Pat<(sub imm64sx32:$imm, GR64:$x),
+                     (SGRK (LGFI imm64sx32:$imm), GR64:$x)>;
+
 // Shift/rotate instructions only use the last 6 bits of the second operand
 // register, so we can safely use NILL (16 fewer bits than NILF) to only AND the
 // last 16 bits.


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