[PATCH] D60427: [ARM] Glue register copies to tail calls.

[Eli Friedman via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL360099: [ARM] Glue register copies to tail calls. (authored by efriedma, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D60427?vs=194220&id=198366#toc

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D60427/new/

https://reviews.llvm.org/D60427

Files:
  llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
  llvm/trunk/test/CodeGen/ARM/tail-call-scheduling.ll


Index: llvm/trunk/test/CodeGen/ARM/tail-call-scheduling.ll
===================================================================
--- llvm/trunk/test/CodeGen/ARM/tail-call-scheduling.ll
+++ llvm/trunk/test/CodeGen/ARM/tail-call-scheduling.ll
@@ -0,0 +1,35 @@
+; RUN: llc < %s | FileCheck %s
+target triple = "armv6kz-unknown-unknown-gnueabihf"
+
+; Make sure this doesn't crash, and we actually emit a tail call.
+; Unfortunately, this test is sort of fragile... the original issue only
+; shows up if scheduling happens in a very specific order. But including
+; it anyway just to demonstrate the issue.
+; CHECK: pop {r4, lr}
+
+ at e = external local_unnamed_addr constant [0 x i32 (i32, i32)*], align 4
+
+; Function Attrs: nounwind sspstrong
+define i32 @AVI_ChunkRead_p_chk(i32 %g) nounwind sspstrong "target-cpu"="arm1176jzf-s" {
+entry:
+  %b = alloca i8, align 1
+  %tobool = icmp eq i32 %g, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  %add = add nsw i32 %g, 1
+  %arrayidx = getelementptr inbounds [0 x i32 (i32, i32)*], [0 x i32 (i32, i32)*]* @e, i32 0, i32 %add
+  %0 = load i32 (i32, i32)*, i32 (i32, i32)** %arrayidx, align 4
+  %call = tail call i32 %0(i32 0, i32 0) #3
+  br label %return
+
+if.end:                                           ; preds = %entry
+  call void @c(i8* nonnull %b)
+  br label %return
+
+return:                                           ; preds = %if.end, %if.then
+  %retval.0 = phi i32 [ %call, %if.then ], [ 0, %if.end ]
+  ret i32 %retval.0
+}
+
+declare void @c(i8*)
Index: llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
+++ llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
@@ -1988,32 +1988,10 @@
   // Build a sequence of copy-to-reg nodes chained together with token chain
   // and flag operands which copy the outgoing args into the appropriate regs.
   SDValue InFlag;
-  // Tail call byval lowering might overwrite argument registers so in case of
-  // tail call optimization the copies to registers are lowered later.
-  if (!isTailCall)
-    for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i) {
-      Chain = DAG.getCopyToReg(Chain, dl, RegsToPass[i].first,
-                               RegsToPass[i].second, InFlag);
-      InFlag = Chain.getValue(1);
-    }
-
-  // For tail calls lower the arguments to the 'real' stack slot.
-  if (isTailCall) {
-    // Force all the incoming stack arguments to be loaded from the stack
-    // before any new outgoing arguments are stored to the stack, because the
-    // outgoing stack slots may alias the incoming argument stack slots, and
-    // the alias isn't otherwise explicit. This is slightly more conservative
-    // than necessary, because it means that each store effectively depends
-    // on every argument instead of just those arguments it would clobber.
-
-    // Do not flag preceding copytoreg stuff together with the following stuff.
-    InFlag = SDValue();
-    for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i) {
-      Chain = DAG.getCopyToReg(Chain, dl, RegsToPass[i].first,
-                               RegsToPass[i].second, InFlag);
-      InFlag = Chain.getValue(1);
-    }
-    InFlag = SDValue();
+  for (unsigned i = 0, e = RegsToPass.size(); i != e; ++i) {
+    Chain = DAG.getCopyToReg(Chain, dl, RegsToPass[i].first,
+                             RegsToPass[i].second, InFlag);
+    InFlag = Chain.getValue(1);
   }
 
   // If the callee is a GlobalAddress/ExternalSymbol node (quite common, every


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