Fix pr6111: Avoid using the LR register for the target address of an indirect

branch in ARM v4 code, since it gets clobbered by the return address before
it is used.  Instead of adding a new register class containing all the GPRs
except LR, just use the existing tGPR class.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96360 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 27 insertions, 4 deletions

diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 6fe7c2c8c6..7b35a06b94 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -643,6 +643,13 @@ ARMBaseInstrInfo::copyRegToReg(MachineBasicBlock &MBB,
   DebugLoc DL = DebugLoc::getUnknownLoc();
   if (I != MBB.end()) DL = I->getDebugLoc();
 
+  // tGPR is used sometimes in ARM instructions that need to avoid using
+  // certain registers.  Just treat it as GPR here.
+  if (DestRC == ARM::tGPRRegisterClass)
+    DestRC = ARM::GPRRegisterClass;
+  if (SrcRC == ARM::tGPRRegisterClass)
+    SrcRC = ARM::GPRRegisterClass;
+
   if (DestRC != SrcRC) {
     if (DestRC->getSize() != SrcRC->getSize())
       return false;
diff --git a/lib/Target/ARM/ARMInstrInfo.td b/lib/Target/ARM/ARMInstrInfo.td
index 1c6f78ac8b..a021388994 100644
--- a/lib/Target/ARM/ARMInstrInfo.td
+++ b/lib/Target/ARM/ARMInstrInfo.td
@@ -828,9 +828,10 @@ let isCall = 1,
   }
 
   // ARMv4T
-  def BX : ABXIx2<(outs), (ins GPR:$func, variable_ops),
+  // Note: Restrict $func to the tGPR regclass to prevent it being in LR.
+  def BX : ABXIx2<(outs), (ins tGPR:$func, variable_ops),
                   IIC_Br, "mov\tlr, pc\n\tbx\t$func",
-                  [(ARMcall_nolink GPR:$func)]>,
+                  [(ARMcall_nolink tGPR:$func)]>,
            Requires<[IsARM, IsNotDarwin]> {
     let Inst{7-4}   = 0b0001;
     let Inst{19-8}  = 0b111111111111;
@@ -865,9 +866,10 @@ let isCall = 1,
   }
 
   // ARMv4T
-  def BXr9 : ABXIx2<(outs), (ins GPR:$func, variable_ops),
+  // Note: Restrict $func to the tGPR regclass to prevent it being in LR.
+  def BXr9 : ABXIx2<(outs), (ins tGPR:$func, variable_ops),
                   IIC_Br, "mov\tlr, pc\n\tbx\t$func",
-                  [(ARMcall_nolink GPR:$func)]>, Requires<[IsARM, IsDarwin]> {
+                  [(ARMcall_nolink tGPR:$func)]>, Requires<[IsARM, IsDarwin]> {
     let Inst{7-4}   = 0b0001;
     let Inst{19-8}  = 0b111111111111;
     let Inst{27-20} = 0b00010010;
diff --git a/test/CodeGen/ARM/call.ll b/test/CodeGen/ARM/call.ll
index 3dd66ae71d..c60b75b574 100644
--- a/test/CodeGen/ARM/call.ll
+++ b/test/CodeGen/ARM/call.ll
@@ -20,3 +20,17 @@ define void @g.upgrd.1() {
         %tmp.upgrd.2 = tail call i32 %tmp( )            ; <i32> [#uses=0]
         ret void
 }
+
+define i32* @m_231b(i32, i32, i32*, i32*, i32*) nounwind {
+; CHECKV4: m_231b
+; CHECKV4: bx r{{.*}}
+BB0:
+  %5 = inttoptr i32 %0 to i32*                    ; <i32*> [#uses=1]
+  %t35 = volatile load i32* %5                    ; <i32> [#uses=1]
+  %6 = inttoptr i32 %t35 to i32**                 ; <i32**> [#uses=1]
+  %7 = getelementptr i32** %6, i32 86             ; <i32**> [#uses=1]
+  %8 = load i32** %7                              ; <i32*> [#uses=1]
+  %9 = bitcast i32* %8 to i32* (i32, i32*, i32, i32*, i32*, i32*)* ; <i32* (i32, i32*, i32, i32*, i32*, i32*)*> [#uses=1]
+  %10 = call i32* %9(i32 %0, i32* null, i32 %1, i32* %2, i32* %3, i32* %4) ; <i32*> [#uses=1]
+  ret i32* %10
+}