[mips][FastISel] Implement FastMaterializeAlloca in Mips fast-isel.

Summary: Implement the method FastMaterializeAlloca in Mips fast-isel

Based on a patch by Reed Kotler.

Test Plan:
Passes test-suite at O0/O2 for mips32 r1/r2
fastalloca.ll

Reviewers: dsanders, rkotler

Subscribers: rfuhler, llvm-commits

Differential Revision: http://reviews.llvm.org/D6742

llvm-svn: 235213

2 files changed, 52 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MipsFastISel.cpp b/llvm/lib/Target/Mips/MipsFastISel.cpp
index 03d5ea2bab7..4b60606eb25 100644
--- a/llvm/lib/Target/Mips/MipsFastISel.cpp
+++ b/llvm/lib/Target/Mips/MipsFastISel.cpp
@@ -187,6 +187,7 @@ public:
     UnsupportedFPMode = Subtarget->isFP64bit();
   }
 
+  unsigned fastMaterializeAlloca(const AllocaInst *AI) override;
   unsigned fastMaterializeConstant(const Constant *C) override;
   bool fastSelectInstruction(const Instruction *I) override;
 
@@ -253,6 +254,25 @@ unsigned MipsFastISel::emitLogicalOp(unsigned ISDOpc, MVT RetVT,
   return ResultReg;
 }
 
+unsigned MipsFastISel::fastMaterializeAlloca(const AllocaInst *AI) {
+  assert(TLI.getValueType(AI->getType(), true) == MVT::i32 &&
+         "Alloca should always return a pointer.");
+
+  DenseMap<const AllocaInst *, int>::iterator SI =
+      FuncInfo.StaticAllocaMap.find(AI);
+
+  if (SI != FuncInfo.StaticAllocaMap.end()) {
+    unsigned ResultReg = createResultReg(&Mips::GPR32RegClass);
+    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Mips::LEA_ADDiu),
+            ResultReg)
+        .addFrameIndex(SI->second)
+        .addImm(0);
+    return ResultReg;
+  }
+
+  return 0;
+}
+
 unsigned MipsFastISel::materializeInt(const Constant *C, MVT VT) {
   if (VT != MVT::i32 && VT != MVT::i16 && VT != MVT::i8 && VT != MVT::i1)
     return 0;
diff --git a/llvm/test/CodeGen/Mips/Fast-ISel/fastalloca.ll b/llvm/test/CodeGen/Mips/Fast-ISel/fastalloca.ll
new file mode 100644
index 00000000000..b4a9f1ce7ab
--- /dev/null
+++ b/llvm/test/CodeGen/Mips/Fast-ISel/fastalloca.ll
@@ -0,0 +1,32 @@
+; RUN: llc -march=mipsel -relocation-model=pic -O0 -mips-fast-isel -fast-isel-abort=1 -mcpu=mips32r2 \
+; RUN:     < %s | FileCheck %s
+
+%struct.x = type { i32 }
+
+@i = common global i32 0, align 4
+
+define i32 @foobar(i32 signext %x) {
+entry:
+; CHECK-LABEL: foobar:
+  %retval = alloca i32, align 4
+  %x.addr = alloca i32, align 4
+  %a = alloca %struct.x, align 4
+  %c = alloca %struct.x*, align 4
+  store i32 %x, i32* %x.addr, align 4
+  %x1 = getelementptr inbounds %struct.x, %struct.x* %a, i32 0, i32 0
+  %0 = load i32, i32* %x.addr, align 4
+  store i32 %0, i32* %x1, align 4
+  store %struct.x* %a, %struct.x** %c, align 4
+  %1 = load %struct.x*, %struct.x** %c, align 4
+  %x2 = getelementptr inbounds %struct.x, %struct.x* %1, i32 0, i32 0
+  %2 = load i32, i32* %x2, align 4
+  store i32 %2, i32* @i, align 4
+  %3 = load i32, i32* %retval
+; CHECK-DAG:    lw      $[[I_ADDR:[0-9]+]], %got(i)($[[REG_GP:[0-9]+]])
+; CHECK-DAG:    addiu   $[[A_ADDR:[0-9]+]], $sp, 8
+; CHECK-DAG:    sw      $[[A_ADDR]], [[A_ADDR_FI:[0-9]+]]($sp)
+; CHECK-DAG:    lw      $[[A_ADDR2:[0-9]+]], [[A_ADDR_FI]]($sp)
+; CHECK-DAG:    lw      $[[A_X:[0-9]+]], 0($[[A_ADDR2]])
+; CHECK-DAG:    sw      $[[A_X]], 0($[[I_ADDR]])
+  ret i32 %3
+}