Avoid folding loads that are unsafe to move.

LiveRangeEdit::foldAsLoad() can eliminate a register by folding a load
into its only use. Only do that when the load is safe to move, and it
won't extend any live ranges.

This fixes PR13414.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160575 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 156 insertions, 0 deletions

diff --git a/lib/CodeGen/LiveRangeEdit.cpp b/lib/CodeGen/LiveRangeEdit.cpp
index 261d860e01..896fdbfbe2 100644
--- a/lib/CodeGen/LiveRangeEdit.cpp
+++ b/lib/CodeGen/LiveRangeEdit.cpp
@@ -177,6 +177,19 @@ bool LiveRangeEdit::foldAsLoad(LiveInterval *LI,
   if (!DefMI || !UseMI)
     return false;
 
+  // Since we're moving the DefMI load, make sure we're not extending any live
+  // ranges.
+  if (!allUsesAvailableAt(DefMI,
+                          LIS.getInstructionIndex(DefMI),
+                          LIS.getInstructionIndex(UseMI)))
+    return false;
+
+  // We also need to make sure it is safe to move the load.
+  // Assume there are stores between DefMI and UseMI.
+  bool SawStore = true;
+  if (!DefMI->isSafeToMove(&TII, 0, SawStore))
+    return false;
+
   DEBUG(dbgs() << "Try to fold single def: " << *DefMI
                << "       into single use: " << *UseMI);
 
diff --git a/test/CodeGen/X86/remat-fold-load.ll b/test/CodeGen/X86/remat-fold-load.ll
new file mode 100644
index 0000000000..de77ad3756
--- /dev/null
+++ b/test/CodeGen/X86/remat-fold-load.ll
@@ -0,0 +1,143 @@
+; RUN: llc < %s -disable-fp-elim -verify-coalescing
+; PR13414
+;
+; During coalescing, remat triggers DCE which deletes the penultimate use of a
+; load. This load should not be folded into the remaining use because it is not
+; safe to move, and it would extend the live range of the address.
+;
+; LiveRangeEdit::foldAsLoad() doesn't extend live ranges, so -verify-coalescing
+; catches the problem.
+
+target triple = "i386-unknown-linux-gnu"
+
+%type_a = type { %type_a*, %type_b }
+%type_b = type { %type_c, i32 }
+%type_c = type { i32, %type_d }
+%type_d = type { i64 }
+%type_e = type { %type_c, i64 }
+
+declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32, i1) nounwind
+
+define linkonce_odr void @test() nounwind {
+entry:
+  br i1 undef, label %while.end.while.end26_crit_edge, label %while.body12.lr.ph
+
+while.end.while.end26_crit_edge:                  ; preds = %entry
+  br label %while.end26
+
+while.body12.lr.ph:                               ; preds = %entry
+  br label %while.body12
+
+while.body12:                                     ; preds = %if.end24, %while.body12.lr.ph
+  %tmp = phi %type_a* [ undef, %while.body12.lr.ph ], [ %tmp18, %if.end24 ]
+  %ins151154161 = phi i128 [ 0, %while.body12.lr.ph ], [ %phitmp, %if.end24 ]
+  %ins135156160 = phi i128 [ 0, %while.body12.lr.ph ], [ %phitmp158, %if.end24 ]
+  %ins151 = or i128 0, %ins151154161
+  %cmp.i.i.i.i.i67 = icmp sgt i32 undef, 8
+  br i1 %cmp.i.i.i.i.i67, label %if.then.i.i.i.i71, label %if.else.i.i.i.i74
+
+if.then.i.i.i.i71:                                ; preds = %while.body12
+  %call4.i.i.i.i68 = call noalias i8* @malloc(i32 undef) nounwind
+  %tmp1 = getelementptr inbounds %type_a* %tmp, i32 0, i32 1, i32 0, i32 1
+  %buf_6.i.i.i.i70 = bitcast %type_d* %tmp1 to i8**
+  %tmp2 = load i8** %buf_6.i.i.i.i70, align 4
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* undef, i8* %tmp2, i32 undef, i32 1, i1 false) nounwind
+  unreachable
+
+if.else.i.i.i.i74:                                ; preds = %while.body12
+  %i_.i.i.i.i72 = getelementptr inbounds %type_a* %tmp, i32 0, i32 1, i32 0, i32 1, i32 0
+  %tmp3 = load i64* %i_.i.i.i.i72, align 4
+  %tmp4 = zext i64 %tmp3 to i128
+  %tmp5 = shl nuw nsw i128 %tmp4, 32
+  %ins148 = or i128 %tmp5, %ins151
+  %second3.i.i76 = getelementptr inbounds %type_a* %tmp, i32 0, i32 1, i32 1
+  %tmp6 = load i32* %second3.i.i76, align 4
+  %tmp7 = zext i32 %tmp6 to i128
+  %tmp8 = shl nuw i128 %tmp7, 96
+  %mask144 = and i128 %ins148, 79228162495817593519834398720
+  %tmp9 = load %type_e** undef, align 4
+  %len_.i.i.i.i86 = getelementptr inbounds %type_e* %tmp9, i32 0, i32 0, i32 0
+  %tmp10 = load i32* %len_.i.i.i.i86, align 4
+  %tmp11 = zext i32 %tmp10 to i128
+  %ins135 = or i128 %tmp11, %ins135156160
+  %cmp.i.i.i.i.i88 = icmp sgt i32 %tmp10, 8
+  br i1 %cmp.i.i.i.i.i88, label %if.then.i.i.i.i92, label %if.else.i.i.i.i95
+
+if.then.i.i.i.i92:                                ; preds = %if.else.i.i.i.i74
+  %call4.i.i.i.i89 = call noalias i8* @malloc(i32 %tmp10) nounwind
+  %ins126 = or i128 0, %ins135
+  %tmp12 = getelementptr inbounds %type_e* %tmp9, i32 0, i32 0, i32 1
+  %buf_6.i.i.i.i91 = bitcast %type_d* %tmp12 to i8**
+  %tmp13 = load i8** %buf_6.i.i.i.i91, align 4
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %call4.i.i.i.i89, i8* %tmp13, i32 %tmp10, i32 1, i1 false) nounwind
+  br label %A
+
+if.else.i.i.i.i95:                                ; preds = %if.else.i.i.i.i74
+  %i_.i.i.i.i93 = getelementptr inbounds %type_e* %tmp9, i32 0, i32 0, i32 1, i32 0
+  br label %A
+
+A:                                                ; preds = %if.else.i.i.i.i95, %if.then.i.i.i.i92
+  %ins135157 = phi i128 [ %ins126, %if.then.i.i.i.i92 ], [ undef, %if.else.i.i.i.i95 ]
+  %second3.i.i97 = getelementptr inbounds %type_e* %tmp9, i32 0, i32 1
+  %tmp14 = load i64* %second3.i.i97, align 4
+  %tmp15 = trunc i64 %tmp14 to i32
+  %cmp.i99 = icmp sgt i32 %tmp6, %tmp15
+  %tmp16 = trunc i128 %ins135157 to i32
+  %cmp.i.i.i.i.i.i101 = icmp sgt i32 %tmp16, 8
+  br i1 %cmp.i.i.i.i.i.i101, label %if.then.i.i.i.i.i103, label %B
+
+if.then.i.i.i.i.i103:                             ; preds = %A
+  unreachable
+
+B:                                                ; preds = %A
+  %tmp17 = trunc i128 %ins148 to i32
+  %cmp.i.i.i.i.i.i83 = icmp sgt i32 %tmp17, 8
+  br i1 %cmp.i.i.i.i.i.i83, label %if.then.i.i.i.i.i85, label %C
+
+if.then.i.i.i.i.i85:                              ; preds = %B
+  unreachable
+
+C:                                                ; preds = %B
+  br i1 %cmp.i99, label %if.then17, label %if.end24
+
+if.then17:                                        ; preds = %C
+  br i1 false, label %if.then.i.i.i.i.i43, label %D
+
+if.then.i.i.i.i.i43:                              ; preds = %if.then17
+  unreachable
+
+D:                                                ; preds = %if.then17
+  br i1 undef, label %if.then.i.i.i.i.i, label %E
+
+if.then.i.i.i.i.i:                                ; preds = %D
+  unreachable
+
+E:                                                ; preds = %D
+  br label %if.end24
+
+if.end24:                                         ; preds = %E, %C
+  %phitmp = or i128 %tmp8, %mask144
+  %phitmp158 = or i128 undef, undef
+  %tmp18 = load %type_a** undef, align 4
+  %tmp19 = load %type_a** undef, align 4
+  %cmp.i49 = icmp eq %type_a* %tmp18, %tmp19
+  br i1 %cmp.i49, label %while.cond10.while.end26_crit_edge, label %while.body12
+
+while.cond10.while.end26_crit_edge:               ; preds = %if.end24
+  %.pre = load %type_e** undef, align 4
+  br label %while.end26
+
+while.end26:                                      ; preds = %while.cond10.while.end26_crit_edge, %while.end.while.end26_crit_edge
+  br i1 undef, label %while.body.lr.ph.i, label %F
+
+while.body.lr.ph.i:                               ; preds = %while.end26
+  br label %while.body.i
+
+while.body.i:                                     ; preds = %while.body.i, %while.body.lr.ph.i
+  br i1 false, label %while.body.i, label %F
+
+F:                                                ; preds = %while.body.i, %while.end26
+  ret void
+}
+
+declare noalias i8* @malloc(i32) nounwind