From b2b03fc2fa87cb5604dd8ec2e8476d051186cdb3 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Fri, 29 Apr 2011 23:34:52 +0000
Subject: [PATCH] Make FastEmit_ri_ try a bit harder to succeed for supported
 operations; FastEmit_i can fail for non-Thumb2 ARM.  Makes ARMSimplifyAddress
 work correctly, and reduces the number of fast-isel bailouts on non-Thumb
 ARM.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130560 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/FastISel.cpp |  9 +++++++--
 test/CodeGen/ARM/fast-isel.ll         | 12 ++++++++++--
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 63e869960bf..3af948288da 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1032,8 +1032,13 @@ unsigned FastISel::FastEmit_ri_(MVT VT, unsigned Opcode,
   if (ResultReg != 0)
     return ResultReg;
   unsigned MaterialReg = FastEmit_i(ImmType, ImmType, ISD::Constant, Imm);
-  if (MaterialReg == 0)
-    return 0;
+  if (MaterialReg == 0) {
+    // This is a bit ugly/slow, but failing here means falling out of
+    // fast-isel, which would be very slow.
+    const IntegerType *ITy = IntegerType::get(FuncInfo.Fn->getContext(),
+                                              VT.getSizeInBits());
+    MaterialReg = getRegForValue(ConstantInt::get(ITy, Imm));
+  }
   return FastEmit_rr(VT, VT, Opcode,
                      Op0, Op0IsKill,
                      MaterialReg, /*Kill=*/true);
diff --git a/test/CodeGen/ARM/fast-isel.ll b/test/CodeGen/ARM/fast-isel.ll
index 81be5978595..6aad92fbc6a 100644
--- a/test/CodeGen/ARM/fast-isel.ll
+++ b/test/CodeGen/ARM/fast-isel.ll
@@ -38,14 +38,22 @@ define void @test2(i32 %tmp, i32* %ptr) nounwind {
 ; ARM: test2:
 
 b1:
-  %b = add i32 %tmp, 4096
-  store i32 %b, i32* %ptr
+  %a = add i32 %tmp, 4096
+  store i32 %a, i32* %ptr
   br label %b2
 
 ; THUMB: add.w {{.*}} #4096
 ; ARM: add {{.*}} #1, #20
 
 b2:
+  %b = add i32 %tmp, 4095
+  store i32 %b, i32* %ptr
+  br label %b3
+; THUMB: addw {{.*}} #4095
+; ARM: movw {{.*}} #4095
+; ARM: add
+
+b3:
   %c = or i32 %tmp, 4
   store i32 %c, i32* %ptr
   ret void