Fix the remaining MUL8 and DIV8 to define AX instead of AL,AH.

These instructions technically define AL,AH, but a trick in X86ISelDAGToDAG
reads AX in order to avoid reading AH with a REX instruction.

Fix PR6489.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97742 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 36 insertions, 8 deletions

diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index cfe71a5acb..d46b9469f1 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -1050,7 +1050,10 @@ def MOV32cr : I<0x22, MRMSrcReg, (outs CONTROL_REG_32:$dst), (ins GR32:$src),
 //
 
 // Extra precision multiplication
-let Defs = [AL,AH,EFLAGS], Uses = [AL] in
+
+// AL is really implied by AX, by the registers in Defs must match the
+// SDNode results (i8, i32).
+let Defs = [AL,EFLAGS,AX], Uses = [AL] in
 def MUL8r  : I<0xF6, MRM4r, (outs),  (ins GR8:$src), "mul{b}\t$src",
                // FIXME: Used for 8-bit mul, ignore result upper 8 bits.
                // This probably ought to be moved to a def : Pat<> if the
@@ -1068,7 +1071,7 @@ def MUL32r : I<0xF7, MRM4r, (outs),  (ins GR32:$src),
                "mul{l}\t$src",
                []>; // EAX,EDX = EAX*GR32
 
-let Defs = [AL,AH,EFLAGS], Uses = [AL] in
+let Defs = [AL,EFLAGS,AX], Uses = [AL] in
 def MUL8m  : I<0xF6, MRM4m, (outs), (ins i8mem :$src),
                "mul{b}\t$src",
                // FIXME: Used for 8-bit mul, ignore result upper 8 bits.
@@ -1090,7 +1093,7 @@ def MUL32m : I<0xF7, MRM4m, (outs), (ins i32mem:$src),
 }
 
 let neverHasSideEffects = 1 in {
-let Defs = [AL,AH,EFLAGS], Uses = [AL] in
+let Defs = [AL,EFLAGS,AX], Uses = [AL] in
 def IMUL8r  : I<0xF6, MRM5r, (outs),  (ins GR8:$src), "imul{b}\t$src", []>;
               // AL,AH = AL*GR8
 let Defs = [AX,DX,EFLAGS], Uses = [AX] in
@@ -1100,7 +1103,7 @@ let Defs = [EAX,EDX,EFLAGS], Uses = [EAX] in
 def IMUL32r : I<0xF7, MRM5r, (outs),  (ins GR32:$src), "imul{l}\t$src", []>;
               // EAX,EDX = EAX*GR32
 let mayLoad = 1 in {
-let Defs = [AL,AH,EFLAGS], Uses = [AL] in
+let Defs = [AL,EFLAGS,AX], Uses = [AL] in
 def IMUL8m  : I<0xF6, MRM5m, (outs), (ins i8mem :$src),
                 "imul{b}\t$src", []>;    // AL,AH = AL*[mem8]
 let Defs = [AX,DX,EFLAGS], Uses = [AX] in
@@ -1113,7 +1116,7 @@ def IMUL32m : I<0xF7, MRM5m, (outs), (ins i32mem:$src),
 } // neverHasSideEffects
 
 // unsigned division/remainder
-let Defs = [AX,EFLAGS], Uses = [AX] in
+let Defs = [AL,EFLAGS,AX], Uses = [AX] in
 def DIV8r  : I<0xF6, MRM6r, (outs),  (ins GR8:$src),    // AX/r8 = AL,AH
                "div{b}\t$src", []>;
 let Defs = [AX,DX,EFLAGS], Uses = [AX,DX] in
@@ -1123,7 +1126,7 @@ let Defs = [EAX,EDX,EFLAGS], Uses = [EAX,EDX] in
 def DIV32r : I<0xF7, MRM6r, (outs),  (ins GR32:$src),   // EDX:EAX/r32 = EAX,EDX
                "div{l}\t$src", []>;
 let mayLoad = 1 in {
-let Defs = [AL,AH,EFLAGS], Uses = [AX] in
+let Defs = [AL,EFLAGS,AX], Uses = [AX] in
 def DIV8m  : I<0xF6, MRM6m, (outs), (ins i8mem:$src),   // AX/[mem8] = AL,AH
                "div{b}\t$src", []>;
 let Defs = [AX,DX,EFLAGS], Uses = [AX,DX] in
@@ -1136,7 +1139,7 @@ def DIV32m : I<0xF7, MRM6m, (outs), (ins i32mem:$src),
 }
 
 // Signed division/remainder.
-let Defs = [AL,AH,EFLAGS], Uses = [AX] in
+let Defs = [AL,EFLAGS,AX], Uses = [AX] in
 def IDIV8r : I<0xF6, MRM7r, (outs),  (ins GR8:$src),    // AX/r8 = AL,AH
                "idiv{b}\t$src", []>;
 let Defs = [AX,DX,EFLAGS], Uses = [AX,DX] in
@@ -1146,7 +1149,7 @@ let Defs = [EAX,EDX,EFLAGS], Uses = [EAX,EDX] in
 def IDIV32r: I<0xF7, MRM7r, (outs),  (ins GR32:$src),   // EDX:EAX/r32 = EAX,EDX
                "idiv{l}\t$src", []>;
 let mayLoad = 1, mayLoad = 1 in {
-let Defs = [AL,AH,EFLAGS], Uses = [AX] in
+let Defs = [AL,EFLAGS,AX], Uses = [AX] in
 def IDIV8m : I<0xF6, MRM7m, (outs), (ins i8mem:$src),   // AX/[mem8] = AL,AH
                "idiv{b}\t$src", []>;
 let Defs = [AX,DX,EFLAGS], Uses = [AX,DX] in
diff --git a/test/CodeGen/X86/2010-03-04-Mul8Bug.ll b/test/CodeGen/X86/2010-03-04-Mul8Bug.ll
new file mode 100644
index 0000000000..48e75e9572
--- /dev/null
+++ b/test/CodeGen/X86/2010-03-04-Mul8Bug.ll
@@ -0,0 +1,25 @@
+; RUN: llc < %s
+; PR6489
+;
+; This test case produces a MUL8 instruction and then tries to read the result
+; from the AX register instead of AH/AL. That confuses live interval analysis.
+;
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin10.0.0"
+
+define void @func_56(i64 %p_57, i32*** %p_58) nounwind ssp {
+for.end:
+  %conv49 = trunc i32 undef to i8                 ; <i8> [#uses=1]
+  %div.i = udiv i8 %conv49, 5                     ; <i8> [#uses=1]
+  %conv51 = zext i8 %div.i to i32                 ; <i32> [#uses=1]
+  %call55 = call i32 @qux(i32 undef, i32 -2) nounwind ; <i32> [#uses=1]
+  %rem.i = urem i32 %call55, -1                   ; <i32> [#uses=1]
+  %cmp57 = icmp uge i32 %conv51, %rem.i           ; <i1> [#uses=1]
+  %conv58 = zext i1 %cmp57 to i32                 ; <i32> [#uses=1]
+  %call85 = call i32 @func_35(i32*** undef, i32 undef, i32 %conv58, i32 1247, i32 0) nounwind ; <i32> [#uses=0]
+  ret void
+}
+
+declare i32 @func_35(i32***, i32, i32, i32, i32)
+
+declare i32 @qux(i32, i32)