ARM: override cost function to re-enable ConstantHoisting (& fix it).

At some point, ARM stopped getting any benefit from ConstantHoisting because
the pass called a different variant of getIntImmCost. Reimplementing the
correct variant revealed some problems, however:

  + ConstantHoisting was modifying switch statements. This is simply invalid,
    the cases must remain integer constants no matter the notional cost.
  + ConstantHoisting was mangling alloca instructions in the entry block. These
    should be handled by FrameLowering, so constants actually have a cost of 0.
    Worse, the resulting bitcasts meant they became dynamic allocas.

rdar://25707382

llvm-svn: 266260

2 files changed, 24 insertions, 2 deletions

diff --git a/llvm/test/CodeGen/ARM/lsr-code-insertion.ll b/llvm/test/CodeGen/ARM/lsr-code-insertion.ll
index aa2b2d26d12..766710fd1d6 100644
--- a/llvm/test/CodeGen/ARM/lsr-code-insertion.ll
+++ b/llvm/test/CodeGen/ARM/lsr-code-insertion.ll
@@ -9,8 +9,8 @@
 ;
 ; CHECK: ldr [[R6:r[0-9*]+]], LCP
 ; CHECK: cmp {{.*}}, [[R6]]
-; CHECK: ldrle
-; CHECK-NEXT: strle
+; CHECK-NOT: lt
+; CHECK: strlt
 
 target triple = "arm-apple-darwin8"
 
diff --git a/llvm/test/CodeGen/ARM/static-addr-hoisting.ll b/llvm/test/CodeGen/ARM/static-addr-hoisting.ll
new file mode 100644
index 00000000000..3d47e02f965
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/static-addr-hoisting.ll
@@ -0,0 +1,22 @@
+; RUN: llc -mtriple=thumbv7-apple-ios %s -o -  | FileCheck %s
+
+define void @multiple_store() {
+; CHECK-LABEL: multiple_store:
+; CHECK: movw r[[BASE1:[0-9]+]], #16960
+; CHECK: movs [[VAL:r[0-9]+]], #42
+; CHECK: movt r[[BASE1]], #15
+
+; CHECK: str [[VAL]], [r[[BASE1]]]
+; CHECK: str [[VAL]], [r[[BASE1]], #24]
+; CHECK: str.w [[VAL]], [r[[BASE1]], #42]
+
+; CHECK: movw r[[BASE2:[0-9]+]], #20394
+; CHECK: movt r[[BASE2]], #18
+
+; CHECK: str [[VAL]], [r[[BASE2]]]
+  store i32 42, i32* inttoptr(i32 1000000 to i32*)
+  store i32 42, i32* inttoptr(i32 1000024 to i32*)
+  store i32 42, i32* inttoptr(i32 1000042 to i32*)
+  store i32 42, i32* inttoptr(i32 1200042 to i32*)
+  ret void
+}