Merging r371111:

------------------------------------------------------------------------ r371111 | efriedma | 2019-09-05 22:02:38 +0200 (Thu, 05 Sep 2019) | 17 lines [IfConversion] Fix diamond conversion with unanalyzable branches. The code was incorrectly counting the number of identical instructions, and therefore tried to predicate an instruction which should not have been predicated. This could have various effects: a compiler crash, an assembler failure, a miscompile, or just generating an extra, unnecessary instruction. Instead of depending on TargetInstrInfo::removeBranch, which only works on analyzable branches, just remove all branch instructions. Fixes https://bugs.llvm.org/show_bug.cgi?id=43121 and https://bugs.llvm.org/show_bug.cgi?id=41121 . Differential Revision: https://reviews.llvm.org/D67203 ------------------------------------------------------------------------ llvm-svn: 371377
llvm · Sep 9, 2019 · 8cdf289 · 8cdf289
1 parent 9523a1c
commit 8cdf289
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Showing 2 changed files with 66 additions and 2 deletions.
diff --git a/llvm/lib/CodeGen/IfConversion.cpp b/llvm/lib/CodeGen/IfConversion.cpp
@@ -1758,9 +1758,15 @@ bool IfConverter::IfConvertDiamondCommon(
   if (!BBI1->IsBrAnalyzable)
     verifySameBranchInstructions(&MBB1, &MBB2);
 #endif
-  BBI1->NonPredSize -= TII->removeBranch(*BBI1->BB);
-  // Remove duplicated instructions.
+  // Remove duplicated instructions from the tail of MBB1: any branch
+  // instructions, and the common instructions counted by NumDups2.
   DI1 = MBB1.end();
+  while (DI1 != MBB1.begin()) {
+    MachineBasicBlock::iterator Prev = std::prev(DI1);
+    if (!Prev->isBranch() && !Prev->isDebugInstr())
+      break;
+    DI1 = Prev;
+  }
   for (unsigned i = 0; i != NumDups2; ) {
     // NumDups2 only counted non-dbg_value instructions, so this won't
     // run off the head of the list.

diff --git a/llvm/test/CodeGen/ARM/ifcvt-diamond-unanalyzable-common.mir b/llvm/test/CodeGen/ARM/ifcvt-diamond-unanalyzable-common.mir
@@ -0,0 +1,58 @@
+# RUN: llc %s -o - -run-pass=if-converter | FileCheck %s
+# Make sure we correctly if-convert blocks containing an INLINEASM_BR.
+# CHECK: t2CMPri killed renamable $r2, 34
+# CHECK-NEXT: $r0 = t2MOVi 2, 1, $cpsr, $noreg
+# CHECK-NEXT: $r0 = t2MOVi 3, 0, killed $cpsr, $noreg, implicit killed $r0
+# CHECK-NEXT: tBL 14, $noreg, @fn2
+# CHECK-NEXT: INLINEASM_BR &"", 9, 13, 0, 13, blockaddress(@fn1, %ir-block.l_yes)
+# CHECK-NEXT: t2B %bb.1, 14, $noreg
+--- |
+  target triple = "thumbv7-unknown-linux-gnueabi"
+
+  define dso_local void @fn1() {
+  l_yes:
+    ret void
+  }
+
+  declare dso_local i32 @fn2(...)
+...
+---
+name:            fn1
+alignment:       1
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    successors: %bb.1(0x40000000), %bb.2(0x40000000)
+    liveins: $r0, $r1, $r2, $r4, $lr
+  
+    $sp = frame-setup t2STMDB_UPD $sp, 14, $noreg, killed $r4, killed $lr
+    t2CMPri killed renamable $r2, 34, 14, $noreg, implicit-def $cpsr
+    t2Bcc %bb.2, 1, killed $cpsr
+  
+  bb.1:
+    successors: %bb.3(0x40000000), %bb.4(0x40000000)
+    liveins: $r1
+  
+    $r0 = t2MOVi 3, 14, $noreg, $noreg
+    tBL 14, $noreg, @fn2, csr_aapcs, implicit-def dead $lr, implicit $sp, implicit $r0, implicit $r1, implicit-def $sp, implicit-def dead $r0
+    INLINEASM_BR &"", 9, 13, 0, 13, blockaddress(@fn1, %ir-block.l_yes)
+    t2B %bb.3, 14, $noreg
+  
+  bb.2:
+    successors: %bb.3(0x40000000), %bb.4(0x40000000)
+    liveins: $r1
+  
+    $r0 = t2MOVi 2, 14, $noreg, $noreg
+    tBL 14, $noreg, @fn2, csr_aapcs, implicit-def dead $lr, implicit $sp, implicit $r0, implicit $r1, implicit-def $sp, implicit-def dead $r0
+    INLINEASM_BR &"", 9, 13, 0, 13, blockaddress(@fn1, %ir-block.l_yes)
+    t2B %bb.3, 14, $noreg
+  
+  bb.3:
+    successors: %bb.4(0x80000000)
+  
+    INLINEASM &"", 1
+  
+  bb.4.l_yes (address-taken):
+    $sp = t2LDMIA_RET $sp, 14, $noreg, def $r4, def $pc
+
+...