Sorry, several patches in one.

TargetInstrInfo:
Change produceSameValue() to take MachineRegisterInfo as an optional argument.
When in SSA form, targets can use it to make more aggressive equality analysis.

Machine LICM:
1. Eliminate isLoadFromConstantMemory, use MI.isInvariantLoad instead.
2. Fix a bug which prevent CSE of instructions which are not re-materializable.
3. Use improved form of produceSameValue.

ARM:
1. Teach ARM produceSameValue to look pass some PIC labels.
2. Look for operands from different loads of different constant pool entries
   which have same values.
3. Re-implement PIC GA materialization using movw + movt. Combine the pair with
   a "add pc" or "ldr [pc]" to form pseudo instructions. This makes it possible
   to re-materialize the instruction, allow machine LICM to hoist the set of
   instructions out of the loop and make it possible to CSE them. It's a bit
   hacky, but it significantly improve code quality.
4. Some minor bug fixes as well.

With the fixes, using movw + movt to materialize GAs significantly outperform the
load from constantpool method. 186.crafty and 255.vortex improved > 20%, 254.gap
and 176.gcc ~10%.

llvm-svn: 123905

1 files changed, 53 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/machine-licm.ll b/llvm/test/CodeGen/ARM/machine-licm.ll
new file mode 100644
index 00000000000..16c15fd2136
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/machine-licm.ll
@@ -0,0 +1,53 @@
+; RUN: llc < %s -mtriple=thumb-apple-darwin -relocation-model=pic -disable-fp-elim | FileCheck %s -check-prefix=THUMB
+; RUN: llc < %s -mtriple=arm-apple-darwin -relocation-model=pic -disable-fp-elim   | FileCheck %s -check-prefix=ARM
+; rdar://7353541
+; rdar://7354376
+
+; The generated code is no where near ideal. It's not recognizing the two
+; constantpool entries being loaded can be merged into one.
+
+@GV = external global i32                         ; <i32*> [#uses=2]
+
+define void @t(i32* nocapture %vals, i32 %c) nounwind {
+entry:
+; ARM: t:
+; ARM: ldr [[REGISTER_1:r[0-9]+]], LCPI0_0
+; ARM-NOT: ldr r{{[0-9]+}}, LCPI0_1
+; ARM: LPC0_0:
+; ARM: ldr r{{[0-9]+}}, [pc, [[REGISTER_1]]]
+; ARM: ldr r{{[0-9]+}}, [r{{[0-9]+}}]
+
+; THUMB: t:
+  %0 = icmp eq i32 %c, 0                          ; <i1> [#uses=1]
+  br i1 %0, label %return, label %bb.nph
+
+bb.nph:                                           ; preds = %entry
+; ARM: LCPI0_0:
+; ARM-NOT: LCPI0_1:
+; ARM: .section
+
+; THUMB: BB#1
+; THUMB: ldr.n r2, LCPI0_0
+; THUMB: add r2, pc
+; THUMB: ldr r{{[0-9]+}}, [r2]
+; THUMB: LBB0_2
+; THUMB: LCPI0_0:
+; THUMB-NOT: LCPI0_1:
+; THUMB: .section
+  %.pre = load i32* @GV, align 4                  ; <i32> [#uses=1]
+  br label %bb
+
+bb:                                               ; preds = %bb, %bb.nph
+  %1 = phi i32 [ %.pre, %bb.nph ], [ %3, %bb ]    ; <i32> [#uses=1]
+  %i.03 = phi i32 [ 0, %bb.nph ], [ %4, %bb ]     ; <i32> [#uses=2]
+  %scevgep = getelementptr i32* %vals, i32 %i.03  ; <i32*> [#uses=1]
+  %2 = load i32* %scevgep, align 4                ; <i32> [#uses=1]
+  %3 = add nsw i32 %1, %2                         ; <i32> [#uses=2]
+  store i32 %3, i32* @GV, align 4
+  %4 = add i32 %i.03, 1                           ; <i32> [#uses=2]
+  %exitcond = icmp eq i32 %4, %c                  ; <i1> [#uses=1]
+  br i1 %exitcond, label %return, label %bb
+
+return:                                           ; preds = %bb, %entry
+  ret void
+}