[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235213 91177308-0d34-0410-b5e6-96231b3b80d8

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
+}