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commit 71002d8a5111d02ce8049c55017a8d948c820e35
Author: Andreas Arnez <arnez@linux.ibm.com>
Date:   Thu Oct 25 13:47:12 2018 +0200

    Bug 400490 s390x: Fix register allocation for VRs vs FPRs
    
    On s390x, if vector registers are available, they are fed to the register
    allocator as if they were separate from the floating-point registers.  But
    in fact the FPRs are embedded in the VRs.  So for instance, if both f3 and
    v3 are allocated and used at the same time, corruption will result.
    
    This is fixed by offering only the non-overlapping VRs, v16 to v31, to the
    register allocator instead.

diff --git a/VEX/priv/host_s390_defs.c b/VEX/priv/host_s390_defs.c
index 6c22ac8..98ac938 100644
--- a/VEX/priv/host_s390_defs.c
+++ b/VEX/priv/host_s390_defs.c
@@ -59,7 +59,6 @@ static UInt s390_tchain_load64_len(void);
 
 /* A mapping from register number to register index */
 static Int gpr_index[16];  // GPR regno -> register index
-static Int fpr_index[16];  // FPR regno -> register index
 static Int vr_index[32];   // VR regno -> register index
 
 HReg
@@ -73,7 +72,7 @@ s390_hreg_gpr(UInt regno)
 HReg
 s390_hreg_fpr(UInt regno)
 {
-   Int ix = fpr_index[regno];
+   Int ix = vr_index[regno];
    vassert(ix >= 0);
    return mkHReg(/*virtual*/False, HRcFlt64, regno, ix);
 }
@@ -463,11 +462,9 @@ getRRegUniverse_S390(void)
 
    RRegUniverse__init(ru);
 
-   /* Assign invalid values to the gpr/fpr/vr_index */
+   /* Assign invalid values to the gpr/vr_index */
    for (UInt i = 0; i < sizeof gpr_index / sizeof gpr_index[0]; ++i)
       gpr_index[i] = -1;
-   for (UInt i = 0; i < sizeof fpr_index / sizeof fpr_index[0]; ++i)
-      fpr_index[i] = -1;
    for (UInt i = 0; i < sizeof vr_index / sizeof vr_index[0]; ++i)
       vr_index[i] = -1;
 
@@ -494,17 +491,17 @@ getRRegUniverse_S390(void)
 
    ru->allocable_start[HRcFlt64] = ru->size;
    for (UInt regno = 8; regno <= 15; ++regno) {
-      fpr_index[regno] = ru->size;
+      vr_index[regno] = ru->size;
       ru->regs[ru->size++] = s390_hreg_fpr(regno);
    }
    for (UInt regno = 0; regno <= 7; ++regno) {
-      fpr_index[regno] = ru->size;
+      vr_index[regno] = ru->size;
       ru->regs[ru->size++] = s390_hreg_fpr(regno);
    }
    ru->allocable_end[HRcFlt64] = ru->size - 1;
 
    ru->allocable_start[HRcVec128] = ru->size;
-   for (UInt regno = 0; regno <= 31; ++regno) {
+   for (UInt regno = 16; regno <= 31; ++regno) {
       vr_index[regno] = ru->size;
       ru->regs[ru->size++] = s390_hreg_vr(regno);
    }
@@ -527,12 +524,12 @@ getRRegUniverse_S390(void)
    /* Sanity checking */
    for (UInt i = 0; i < sizeof gpr_index / sizeof gpr_index[0]; ++i)
       vassert(gpr_index[i] >= 0);
-   for (UInt i = 0; i < sizeof fpr_index / sizeof fpr_index[0]; ++i)
-      vassert(fpr_index[i] >= 0);
    for (UInt i = 0; i < sizeof vr_index / sizeof vr_index[0]; ++i)
       vassert(vr_index[i] >= 0);
                  
    initialised = True;
+
+   RRegUniverse__check_is_sane(ru);
    return ru;
 }