[PATCH] D16687: Fix for PR26356

[Nemanja Ivanovic via llvm-commits]

nemanjai created this revision.
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Fast Isel fails when trying to load an unsigned immediate greater than 0x7FFF. The li instruction takes a signed immediate so it isn't appropriate for such values.

Repository:
  rL LLVM

http://reviews.llvm.org/D16687

Files:
  lib/Target/PowerPC/PPCFastISel.cpp
  test/CodeGen/PowerPC/pr26356.ll

Index: test/CodeGen/PowerPC/pr26356.ll
===================================================================
--- test/CodeGen/PowerPC/pr26356.ll
+++ test/CodeGen/PowerPC/pr26356.ll
@@ -0,0 +1,10 @@
+; RUN: llc -mcpu=pwr7 -mtriple=powerpc64le-unknown-unknown -O0 < %s | FileCheck %s
+
+; Function Attrs: nounwind
+define internal zeroext i16 @zot() #0 {
+  ret i16 32768
+}
+
+; CHECK: li 3, 0
+; CHECK: ori 3, 3, 32768
+; CHECK: blr
Index: lib/Target/PowerPC/PPCFastISel.cpp
===================================================================
--- lib/Target/PowerPC/PPCFastISel.cpp
+++ lib/Target/PowerPC/PPCFastISel.cpp
@@ -2100,6 +2100,19 @@
         .addImm(CI->getSExtValue());
     return ImmReg;
   } else if (!UseSExt && isUInt<16>(CI->getZExtValue())) {
+    // The li instruction loads signed 16-bit immediates so we
+    // need an extra step for unsigned values with the high bit set.
+    if (CI->getZExtValue() > 0x7FFF) {
+      unsigned LdImm = (VT == MVT::i64) ? PPC::LI8 : PPC::LI;
+      unsigned OrImm = (VT == MVT::i64) ? PPC::ORI8 : PPC::ORI;
+      unsigned ResReg = createResultReg(RC);
+      unsigned TmpReg = createResultReg(RC);
+      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(LdImm), TmpReg)
+          .addImm(0);
+      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(OrImm), ResReg)
+          .addReg(TmpReg).addImm(CI->getZExtValue());
+      return ResReg;
+    }
     unsigned Opc = (VT == MVT::i64) ? PPC::LI8 : PPC::LI;
     unsigned ImmReg = createResultReg(RC);
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc), ImmReg)


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