[PATCH] D46582: [PowerPC] Fix label address calculation for ppc32

[Strahinja Petrovic via Phabricator via llvm-commits]

spetrovic created this revision.
spetrovic added reviewers: joerg, jhibbits, nemanjai.
Herald added subscribers: llvm-commits, kbarton.

This patch fixes calculating address of label on ppc32 (for -fPIC), I was using gcc as reference. You can try to run this example with and without the patch and see the difference:

unsigned int foo(void) {

  return 0;

}

int main() {
L: __attribute__ ((unused));

  static const unsigned int arr[] =
  {
    (unsigned int) &&x  - (unsigned int)&&L ,
    (unsigned int) &&y  - (unsigned int)&&L
  };
  
  unsigned int ret = foo();
  void* g = (void *) ((unsigned int)&&L + arr[ret]);
  goto *g;

x:

  return 15;

y:

  return 25;

}


Repository:
  rL LLVM

https://reviews.llvm.org/D46582

Files:
  lib/Target/PowerPC/PPCISelLowering.cpp
  test/CodeGen/PowerPC/ppc-label.ll


Index: test/CodeGen/PowerPC/ppc-label.ll
===================================================================
--- test/CodeGen/PowerPC/ppc-label.ll
+++ test/CodeGen/PowerPC/ppc-label.ll
@@ -0,0 +1,44 @@
+; RUN: llc < %s -mtriple=powerpc-unknown-linux-gnu -relocation-model=pic | FileCheck %s
+
+; unsigned int foo(void) {
+;   return 0;
+; }
+;
+; int main() {
+; L: __attribute__ ((unused));
+;   static const unsigned int arr[] =
+;   {
+;     (unsigned int) &&x  - (unsigned int)&&L ,
+;     (unsigned int) &&y  - (unsigned int)&&L
+;   };
+;
+;   unsigned int ret = foo();
+;   void* g = (void *) ((unsigned int)&&L + arr[ret]);
+;   goto *g;
+;
+; x:
+;   return 15;
+; y:
+;   return 25;
+; }
+
+define i32 @foo() local_unnamed_addr {
+entry:
+  ret i32 0
+}
+
+define i32 @main() {
+entry:
+  br label %L
+
+L:                                                ; preds = %L, %entry
+  indirectbr i8* inttoptr (i32 add (i32 ptrtoint (i8* blockaddress(@main, %L) to i32), i32 sub (i32 ptrtoint (i8* blockaddress(@main, %return) to i32), i32 ptrtoint (i8* blockaddress(@main, %L) to i32))) to i8*), [label %return, label %L]
+
+return:                                           ; preds = %L
+  ret i32 15
+}
+
+
+; CHECK:     lwz 3, .LC0-.LTOC(30)
+; CHECK-NOT: li 3, .Ltmp1-.L1$pb at l
+; CHECK-NOT: addis 4, 30, .Ltmp1-.L1$pb at ha
\ No newline at end of file
Index: lib/Target/PowerPC/PPCISelLowering.cpp
===================================================================
--- lib/Target/PowerPC/PPCISelLowering.cpp
+++ lib/Target/PowerPC/PPCISelLowering.cpp
@@ -2566,10 +2566,10 @@
 
   // 64-bit SVR4 ABI code is always position-independent.
   // The actual BlockAddress is stored in the TOC.
-  if (Subtarget.isSVR4ABI() && Subtarget.isPPC64()) {
+  if (Subtarget.isSVR4ABI() && isPositionIndependent()) {
     setUsesTOCBasePtr(DAG);
     SDValue GA = DAG.getTargetBlockAddress(BA, PtrVT, BASDN->getOffset());
-    return getTOCEntry(DAG, SDLoc(BASDN), true, GA);
+    return getTOCEntry(DAG, SDLoc(BASDN), Subtarget.isPPC64(), GA);
   }
 
   unsigned MOHiFlag, MOLoFlag;


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