[ARM] Fix handling of thumb1 out-of-range frame offsets

LocalStackSlotPass assumes that isFrameOffsetLegal doesn't change its
answer when the base register changes. Unfortunately this isn't true
in thumb1, where SP-based loads allow a larger offset than
non-SP-based loads, and this causes the base register reuse code to
generate instructions that are unencodable, causing an assertion
failure. 

Solve this by adding a BaseReg parameter to isFrameOffsetLegal, which
ARMBaseRegisterInfo can then make use of to give the correct answer. 

Differential Revision: http://reviews.llvm.org/D8419

llvm-svn: 232825

1 files changed, 7 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp b/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
index e8bf687..8378429 100644
--- a/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
+++ b/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
@@ -252,7 +252,8 @@ void LocalStackSlotPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
 }
 
 static inline bool
-lookupCandidateBaseReg(int64_t BaseOffset,
+lookupCandidateBaseReg(unsigned BaseReg,
+                       int64_t BaseOffset,
                        int64_t FrameSizeAdjust,
                        int64_t LocalFrameOffset,
                        const MachineInstr *MI,
@@ -260,7 +261,7 @@ lookupCandidateBaseReg(int64_t BaseOffset,
   // Check if the relative offset from the where the base register references
   // to the target address is in range for the instruction.
   int64_t Offset = FrameSizeAdjust + LocalFrameOffset - BaseOffset;
-  return TRI->isFrameOffsetLegal(MI, Offset);
+  return TRI->isFrameOffsetLegal(MI, BaseReg, Offset);
 }
 
 bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
@@ -362,8 +363,9 @@ bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
     // instruction itself will be taken into account by the target,
     // so we don't have to adjust for it here when reusing a base
     // register.
-    if (UsedBaseReg && lookupCandidateBaseReg(BaseOffset, FrameSizeAdjust,
-                                              LocalOffset, MI, TRI)) {
+    if (UsedBaseReg && lookupCandidateBaseReg(BaseReg, BaseOffset,
+                                              FrameSizeAdjust, LocalOffset, MI,
+                                              TRI)) {
       DEBUG(dbgs() << "  Reusing base register " << BaseReg << "\n");
       // We found a register to reuse.
       Offset = FrameSizeAdjust + LocalOffset - BaseOffset;
@@ -382,7 +384,7 @@ bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
       // then don't bother creating it.
       if (ref + 1 >= e ||
           !lookupCandidateBaseReg(
-              BaseOffset, FrameSizeAdjust,
+              BaseReg, BaseOffset, FrameSizeAdjust,
               FrameReferenceInsns[ref + 1].getLocalOffset(),
               FrameReferenceInsns[ref + 1].getMachineInstr(), TRI)) {
         BaseOffset = PrevBaseOffset;