Reapply r174343, with a fix for a scary DAG combine bug where it failed to differenti...

base point of a load, and the overall alignment of the load.  This caused infinite loops in DAG combine with the
original application of this patch.

ORIGINAL COMMIT LOG:
When the target-independent DAGCombiner inferred a higher alignment for a load,
it would replace the load with one with the higher alignment.  However, it did
not place the new load in the worklist, which prevented later DAG combines in
the same phase (for example, target-specific combines) from ever seeing it.

This patch corrects that oversight, and updates some tests whose output changed
due to slightly different DAGCombine outputs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174431 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 79ec227a22b2c7b87ac451db08cd91768d5dd112..d694bc782c0235e652cca5730e33f5362f109b66 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7199,12 +7199,15 @@ SDValue DAGCombiner::visitLOAD(SDNode *N) {
   // Try to infer better alignment information than the load already has.
   if (OptLevel != CodeGenOpt::None && LD->isUnindexed()) {
     if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
-      if (Align > LD->getAlignment())
-        return DAG.getExtLoad(LD->getExtensionType(), N->getDebugLoc(),
+      if (Align > LD->getMemOperand()->getBaseAlignment()) {
+        SDValue NewLoad =
+               DAG.getExtLoad(LD->getExtensionType(), N->getDebugLoc(),
                               LD->getValueType(0),
                               Chain, Ptr, LD->getPointerInfo(),
                               LD->getMemoryVT(),
                               LD->isVolatile(), LD->isNonTemporal(), Align);
+        return CombineTo(N, NewLoad, SDValue(NewLoad.getNode(), 1), true);
+      }
     }
   }
 

diff --git a/test/CodeGen/AArch64/func-argpassing.ll b/test/CodeGen/AArch64/func-argpassing.ll
index db58798ca5511bb12e93710bc8acf9326a56d04a..760c8d49d07bf8e2cdd6934284b223c6a7094298 100644 (file)
--- a/test/CodeGen/AArch64/func-argpassing.ll
+++ b/test/CodeGen/AArch64/func-argpassing.ll
@@ -178,7 +178,8 @@ define void @check_i128_stackalign(i32 %val0, i32 %val1, i32 %val2, i32 %val3,
     ; Nothing local on stack in current codegen, so first stack is 16 away
 ; CHECK: ldr {{x[0-9]+}}, [sp, #16]
     ; Important point is that we address sp+24 for second dword
-; CHECK: ldr {{x[0-9]+}}, [sp, #24]
+; CHECK: add     [[REG:x[0-9]+]], sp, #16
+; CHECK: ldr     {{x[0-9]+}}, {{\[}}[[REG]], #8]
     ret void
 }
 

diff --git a/test/CodeGen/X86/divide-by-constant.ll b/test/CodeGen/X86/divide-by-constant.ll
index 8e7c13d8efa9cdc706e8db05e5a6aed7482c1e18..9669d97cb7fa2b850b2b10d5f4249afba98b3a5a 100644 (file)
--- a/test/CodeGen/X86/divide-by-constant.ll
+++ b/test/CodeGen/X86/divide-by-constant.ll
@@ -56,9 +56,9 @@ entry:
   %div = sdiv i16 %x, 10
   ret i16 %div
 ; CHECK: test6:
-; CHECK: imull $26215, %eax, %eax
-; CHECK: shrl  $31, %ecx
-; CHECK: sarl  $18, %eax
+; CHECK: imull $26215, %eax, %ecx
+; CHECK: sarl $18, %ecx
+; CHECK: shrl $15, %eax
 }
 
 define i32 @test7(i32 %x) nounwind {